Starting with its discovery in 1929, the stable nuclide 13C has been a critical tool for developing our understanding of photosynthesis. Early surveys of carbon isotopes in plants led to questions about whether the isotopic ratio of a given plant is ultimately controlled by an active response to its environment or by the relatively static biochemistry of photosynthesis. This led to a model of the carbon isotope composition of plant tissue meant to describe the integrated effects of physical diffusion, the biochemical action of enzymes, and the physiological response of stomata on net carbon fixation. In the decades since, recognition of the CO2 rise has highlighted the role of photorespiration, inviting a more thorough analysis to isolate the effect of CO2 concentration on 13C uptake and fixation. Plant growth chamber experiments performed across multiple levels of CO2 quantified the dependency of net carbon isotope discrimination on CO2, and showed the effect to be both significant and independent of the effect of water limitation. These advances pave the way for the determination of ancient CO2 levels from the stable isotope composition of fossilized plant remains, particularly for understudied, yet fossil-rich, periods of geologic time.
Within the plant endomembrane system, the vesicle coat protein clathrin localizes to the plasma membrane (PM) and the trans-Golgi Network/early endosome (TGN/EE). While the role of clathrin in endocytosis at the PM is well established, its function at TGN/EE, presumably in late secretion (trafficking from the TGN/EE to the cell surface) or en route to the vacuole, is debated. Similarly debated are potential homeostatic mechanisms balancing the trafficking routes, especially endocytosis and late secretion. We address these questions in Arabidopsis thaliana using conditional silencing of CLATHRIN HEAVY CHAIN (CHC), conditional overexpression of the clathrin uncoating factor AUXILIN-LIKE1, and secretory mutants. CHC silencing interferes with trafficking of cargoes destined for the apoplast and the PM, supporting a function of clathrin in late secretion. The secretory cargoes become abnormally rerouted from the TGN/EE to the vacuole. Unlike CHC silencing, overexpression of AUXILIN-LIKE1 selectively inhibits clathrin-mediated endocytosis while secretion continues normally at early points of induction. Conversely, secretory mutants exhibit a reduced PM recruitment of clathrin, and variably, of the TPLATE endocytic component. Together, our data show a role of clathrin in secretion and suggest secretion as a fundamental trafficking process to which endocytosis is adjusted by a weak homeostatic mechanism.
The process of State Transitions (ST) corresponds to an STT7 kinase-driven redistribution of the transmembrane LHCII antenna proteins between Photosystem II (PSII) and Photosystem I (PSI), which results from changes in their phosphorylation state. For the past two decades, two LHCII-kinase mutants, stt7-1 and stt7-9, have been instrumental in the study of STs in Chlamydomonas reinhardtii, the former being a null mutant for the kinase but quasi-sterile in crosses, while the latter, although fertile, has a leaky phenotype. Using long-read sequencing, this study further characterized the genetic lesions of the stt7 mutant strains through whole-genome reconstruction and de novo chromosome assembly. In addition, two new stt7 null mutants were generated, one derived by crosses from the original stt7-1 and one obtained by Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated protein 9 (Cas9) technology. This work provides a comprehensive genomic characterization of the original stt7-1 null mutant, revealing extensive chromosomal rearrangements and high levels of aneuploidy, associated with increased cell size and meiotic dysfunction. Reassessment of their physiology and genetic backgrounds highlights the need for caution in interpreting genetic information. We thus produced more reliable null mutants for the LHCII-kinase, amenable to genetic crosses for the study of STs in a variety of genetic backgrounds.
The SNF1-related protein kinase 2 (SnRK2) pathway is a central regulator of abiotic stress signaling in land plants, yet its evolutionary origins and functional conservation across the green lineage remain poorly understood. To determine whether this signaling module predates the streptophyte-chlorophyte divergence, we investigated the chlorophyte alga Chlamydomonas reinhardtii, which diverged from the streptophyte lineage over 1 billion years ago. Using a combination of reverse genetics and protein-protein interaction assays, we identified and characterized a bona fide SnRK2 signaling module in C. reinhardtii. We demonstrate that the isoform SnRK2.7 is essential for osmotic stress tolerance and general cellular viability. SnRK2.7 localizes to the contractile vacuole, an osmoregulatory organelle lost during streptophyte evolution, revealing a lineage-specific functional adaptation. Together with MAPKKK3, a B1/B3-RAF kinase, and the clade A protein phosphatase PP2C3, these components constitute a MAPKKK3-SnRK2.7-PP2C3 regulatory module in C. reinhardtii. Our findings demonstrate the presence of a functional SnRK2 pathway in a chlorophyte alga, suggesting that core components were established early in the green lineage. This work provides a foundation for comparative studies across green plants and underscores the need for broader taxonomic sampling to reconstruct the ancestral signaling networks underlying stress adaptation. SNF1相关蛋白激酶2(SnRK2)信号通路是陆地植物非生物胁迫信号转导的核心调控网络，但其在绿色植物谱系中的进化起源及功能保守性尚不清楚。为探究该信号模块是否早于链形植物与绿藻的分化事件而存在，本研究以莱茵衣藻(Chlamydomonas reinhardtii)为研究对象，该物种于约十亿年前从链形植物谱系分化而来。 通过反向遗传学与蛋白质互作分析，我们在莱茵衣藻中鉴定并表征了一个功能性的SnRK2信号模块。 结果表明，该激酶家族成员SnRK2.7对渗透胁迫耐受性及细胞长期存活至关重要；SnRK2.7蛋白定位于伸缩泡——一种在链形植物进化中丢失的渗透调节细胞器，提示该蛋白在绿色植物谱系演化中获得了特异性功能适应。进一步研究发现，SnRK2.7与MAPKKK3(一种B1/B3类RAF蛋白激酶)及A亚类PP2C蛋白磷酸酶PP2C3共同组成莱茵衣藻中的MAPKKK3‐SnRK2.7‐PP2C3调控模块。 本研究首次证明绿藻中存在功能性的SnRK2通路，表明该通路的核心组分在绿色植物早期进化中即已建立。该工作为理解植物非生物胁迫信号通路的进化起源提供了关键证据，同时强调了扩大系统发育类群研究对重建祖先胁迫适应网络不可或缺的重要性。.
The control of cell division plane orientation is fundamental for organizing developmental processes and shaping bodies of multicellular organisms. In plants, radial organ growth is mediated by the cambium, a stem cell niche embedded in expanding organs and continuously producing xylem and phloem in a strictly bidirectional manner. Cambium stem cells (CSCs) are unique in comparison with other plant stem cells as they consistently divide along their longest axis, clearly overriding the commonly found 'short axis' rule. Here, we investigated how cell division plane orientation is controlled in Arabidopsis thaliana (Arabidopsis) CSCs. We characterized successive microtubule organization during CSC divisions using immunolabelling and histologically compared wild-type, preprophase band (PPB)-deficient, and cortical division zone (CDZ)-deficient mutants. We found that division plane orientation is established independently from spindle orientation and the PPB. Instead, the orientation of division planes depends on the CDZ and CDZ-related PHRAGMOPLAST ORIENTING KINESIN (POK) proteins. Robust CSC division orientation is independent of the PPB, challenging the view that the PPB is universally required to stabilize plant cell divisions. Our results highlight the importance of wood-forming CSCs and their subcellular characterization as an instructive example for the determination of cell division orientation in plants.
Root-knot nematodes (Meloidogyne spp.) secrete effectors that suppress plant immunity; however, the mechanisms by which they counteract specific defense enzymes, such as chitinases, remain unclear. In this study, we demonstrate that the Meloidogyne incognita effector Minc10750 directly targets the catalytic domain of plant chitinases (Chi), serving as a critical determinant of virulence. The expression of Minc10750 is upregulated in the subventral esophageal glands during early infection. Its binding to the glycosyl hydrolase 19 domain of chitinases is strictly dependent on effector N-glycosylation. A mutation at the asparagine glycosylation site (Minc10750-Mu3) abolishes this modification, impairs its nuclear accumulation, and disrupts the interaction. Mechanistically, Minc10750 promotes the proteasome-dependent destabilization of Chi proteins, thereby suppressing Chi-triggered immunity, including mitogen‑activated protein kinase (MAPK) activation and reactive oxygen species burst. Consistently, Chi mutants exhibit enhanced susceptibility to nematodes, whereas Chi overexpression confers resistance. Transcriptome analysis further reveals that the Chi-mediated expression of defense-related transcription factors is compromised in Minc10750 transgenic plants. Our findings elucidate a mechanism by which a glycosylated nematode effector disables a core component of basal immunity, thereby providing a potential target for the engineering of nematode-resistant crops.
Enhancing lipid accumulation by redirecting carbon from starch to triacylglycerol (TAG) in vegetative tissues is a promising strategy for developing high-energy-density crops for bioenergy production. However, our understanding of how starch and TAG metabolism interact and how this interaction affects growth and photosynthesis is incomplete. Here, we investigated the metabolic and physiological consequences of disrupting starch biosynthesis and TAG turnover in Arabidopsis thaliana by generating single, double, and triple mutants involving ADG1 (starch biosynthesis), TGD1 (lipid trafficking), and SDP1 (TAG lipase). Unexpectedly, elimination of starch biosynthesis lowered TAG levels in the high-TAG-accumulating tgd1 mutant, primarily through enhanced TAG breakdown. This decline was completely reversed by sucrose supplementation, suggesting that TAG degradation was induced by carbon limitation. Genetic suppression of TAG turnover via SDP1 disruption in the starchless tgd1 adg1-1 background led to a nine-fold rise in leaf TAG accumulation in the tgd1 sdp1 adg1-1 triple mutant, together with enhanced photosynthetic performance. However, this metabolic reprogramming incurred growth penalties. Our results highlight the role of dynamic TAG turnover in maintaining metabolic balance and photosynthesis in starch-deficient backgrounds. These findings underscore the need for refined metabolic engineering strategies that coordinate TAG biosynthesis and degradation to optimize lipid accumulation in bioenergy crops.
Seeking universal rules that govern leaf size variation is a long-standing aspiration in ecology. Early studies propose that the inverse of the product of leaf tissue density and thickness, termed the Hughes constant, is approximately conserved within species, which renders the ratio of leaf area (An) to fresh mass (m) invariant. We tested this proposition with an unprecedented dataset encompassing c. 157 000 leaves from 335 woody species across China. Using the allometric model A n = c · m α , we assessed for each species whether α  = 1, as required for a constant An : m. We further examined whether and how α and An : m varied across plant habits and climate regimes. The grand mean (0.923) of α across species was significantly lower than unity, and 69% of species exhibited α  < 1, indicating diminishing returns of leaf area on increasing fresh-mass investments. Notably, evergreen species exhibited lower An : m ratios (higher construction costs per unit area) but higher α values (greater returns to scale) than deciduous species. Climatic factors explained little variation of α, but higher temperatures were associated with lower An : m ratios. Altogether, the Hughes constant represents an approximate tendency rather than a universal rule. Yet, An : m ratios are highly species-specific, bearing a functional significance in discriminating plant habits and thermal niches.
The plant-parasitic nematode Meloidogyne incognita is the pathogen with the broadest host range among all known biotrophic interactions. This species is also the single most damaging of a group of agriculturally important plant parasites, which together are estimated to contribute to losses in excess of $170 billion yr-1 to world agriculture. Understanding how M. incognita is able to infect representatives from most orders of flowering plants, covering more than 3000 species, addresses a fundamentally important question of how pathogens adapt to their host-environment, and may inform control of a pathogen, which threatens global food security. Here, we analyse the plant-nematode infection phenotype and cross-kingdom transcriptome of nine interactions across six orders of flowering plants at 25 d post infection. Our data show that the phylogenetic distribution of hosts does not explain the phenotypic distribution of parasitism. Three distinct nematode 'transcriptional programmes' are evident, and we find that effectors are neither uniformly deployed across hosts nor across groups of hosts. Nevertheless, this differential deployment of effectors can determine host specificity. Finally, we show that there is no widespread core gall transcriptome at 25 d post infection, prompting the proposal of a model best described as 'all roads lead to Rome'.
Understanding why the Neotropics are one of the most biodiverse regions on earth remains a major challenge in ecology and evolutionary biology. We still know little about how the complex interplay between the geological history, climatic fluctuations, and interspecific interactions has led to the build-up of present-day diversity patterns. Here, we explore patterns of diversification in the diverse palm genus Geonoma, encompassing nearly 70 species throughout Central and South America, using phylogenetic analyses, models of diversification and phenotypic evolution. The clade originated in the Andes and subsequently dispersed toward Amazonia and Central America. The speciation rate has been constantly declining through time, possibly related to temperature cooling or increased interspecific competition for resources. We also found an exceptionally high disparity for 28 traits suggesting potential niche partitioning and character displacement, a result partially supported by models of phenotypic evolution. Overall, our study unravels the influence of geological, abiotic, and biotic factors at different stages of the diversification process of Geonoma and illustrates how their complex interactions contribute to the buildup of neotropical diversity. Comprendre pourquoi les Néotropiques sont une des régions les plus diverses du monde demeure un défi majeur en écologie et biologie évolutive. Nous savons encore peu sur les rôles de l’histoire géologique, des fluctuations climatiques et des interactions interspécifiques qui ont conduit à la construction des patrons de diversité actuels. Dans cette étude, nous explorons les dynamiques de diversification du genre de palmiers Geonoma, comprenant près de 70 espèces réparties en Amérique du Sud et en Amérique Centrale, en utilisant des analyses phylogénétiques, des modèles de diversification et d’évolution phénotypique. Le clade s’est diversifié originellement dans les Andes et a ensuite colonisé l’Amazonie et l’Amérique Centrale. Le taux de spéciation a diminué progressivement au cours du temps. Nous proposons deux causes potentielles de ce déclin: un refroidissement climatique ou une augmentation de la compétition interspécifique pour les ressources. En accord avec l’hypothèse de compétition, nous avons également trouvé une disparité exceptionnelle pour 28 traits morphologiques et climatiques suggérant un partitionnement de niche et un déplacement de caractère, un résultat partiellement supporté par nos modèles d’évolution phénotypique. En conclusion, notre étude met en lumière l’influence des facteurs géologiques, abiotiques et biotiques à différentes phases du processus de diversification de Geonoma et illustre comment l’interaction de ces facteurs contribue à l’évolution de la diversité néotropicale.
In the green microalga Chlamydomonas reinhardtii, UV-B radiation triggers complex photoprotective mechanisms. While Light-Harvesting Complex Stress Related 1 (LHCSR1) has been traditionally viewed as the primary UV-B responsive protein, the functional significance of LHCSR3 and its interplay with the STT7 kinase under these conditions remain largely elusive. Here, we investigated the spectral and structural dynamics of thylakoid supercomplexes under continuous long-term UV-B irradiation using a comparative approach with wild-type, npq4 (LHCSR3-deficient), stt7-9 (STT7 kinase-deficient), and npq4 stt7-9 double-mutant strains. Our results demonstrate that UV-B induces substantial accumulation of both LHCSR1 and LHCSR3, yet only LHCSR3 undergoes STT7-dependent phosphorylation. This modification is essential for the formation of high-molecular-weight PSII-LHCII megacomplexes and a specialized PSI-LHCI-LHCII-LHCSRs supercomplex during state transitions. In the absence of LHCSR3, both photosystem core subunits and peripheral antennae (CP26/CP29) undergo extensive degradation. We further identified that STT7 kinase is required for antenna detachment and facilitates stable LHCSR3 accumulation. LHCSR3 is a dual-function regulator indispensable for both energy quenching and structural stabilization of the photosynthetic apparatus. The STT7-LHCSR3 mechanism represents a vital adaptive strategy that primes the machinery for fluctuating light environments.
Water is essential for life on Earth, yet some plants can survive the near-complete loss of cellular water, a trait known as desiccation tolerance. Although rare in vegetative tissues of vascular plants, desiccation tolerance is scattered across the plant kingdom, where it likely enabled early terrestrialization and supports survival in environments with prolonged or intermittent drying. Large-scale multi-omics, comparative, and functional studies over the past decade suggest that desiccation tolerance evolved primarily through the repurposing of ancient stress-resilience mechanisms, giving rise to convergent phenotypes where cells are protected and stabilized during extreme dehydration. In photosynthetic lineages, desiccation is further compounded by light-dependent photooxidative stress, requiring specialized mechanisms that safeguard the photosynthetic apparatus during both drying and recovery. Here, we synthesize our current understanding of the evolutionary origins and core mechanisms underlying plant desiccation tolerance and place them within a broader comparative context across kingdoms. We highlight how genome-scale datasets suggest desiccation tolerance is an emergent, systems-level phenotype coordinated across biological scales. Finally, we discuss the translational opportunities and constraints of desiccation tolerance in agriculture, medicine, biotechnology, and related fields.
Cytoplasmic male sterility (CMS) is widely used in rapeseed hybrid breeding. The Polima (pol) CMS system is associated with the mitochondrial chimeric gene orf224, yet how it disrupts early anther differentiation and leads to sterility remains unclear. We combined cytological analyses, ultrastructural observations, transcriptomics, proteomics, and metabolomics to examine young anther development in pol CMS, maintainer, and restorer lines, with particular focus on mitochondrial function, metabolism, and hormone homeostasis. In pol CMS, L2-derived anther cells failed to differentiate into the middle layer, tapetum, and microspore mother cells, with development arrested at stage S5. The ORF224 protein preferentially accumulated in young anthers and exhibited cytotoxicity, causing mitochondrial dysfunction, reduced ATP production, and activation of mitochondrial retrograde signaling. These changes induced extensive metabolic reprogramming, including ectopic activation of photosynthesis-like reaction, starch accumulation, elevated ROS, and a pronounced increase in abscisic acid (ABA). Our results demonstrate that pol CMS sterility results from ORF224-mediated mitochondrial stress that reprograms anther cell fate from reproductive to somatic development, with ABA reinforcing developmental arrest, while programmed cell death occurs as a late downstream consequence.
Potassium (K+) deficiency severely limits global wheat productivity and food security. Genetic improvement of K+ utilization efficiency (KUE) is a sustainable strategy to address this challenge; however, the underlying molecular mechanisms remain unclear. We identified a lncRNA62732-miR9778-TaHAK18-5B module in wheat (Triticum aestivum) using long noncoding RNAs (lncRNA)-sequencing combined with competing endogenous RNA prediction. Using genetic transformation and molecular biology techniques, we analyzed the role of this module in mediating the response to K+ deficiency and the mechanisms underlying its effects. miR9778 is a Triticeae-specific miRNA that directly targets TaHAK18-5B. Both miR9778 silencing and TaHAK18-5B overexpression notably enhanced K+ deficiency tolerance at the seedling stage by modulating root K+ acquisition and translocation from the roots to the shoots, whereas silencing TaHAK18-5B had the opposite effect. Additionally, lncRNA62732 was identified as an endogenous target mimic (eTM) of miR9778 that sequesters miR9778 and prevents miR9778-mediated cleavage of TaHAK18-5B, thereby positively regulating wheat seedlings' growth under K+ deficiency conditions. Notably, the lncRNA62732-miR9778-TaHAK18-5B module improved wheat adaptation to K+ deficiency and enhanced the KUE and grain yield under field conditions. These results reveal a novel module in mediating K+ homeostasis and provide valuable genetic resources for engineering KUE in wheat.
Alpine treelines mark the physiological limit to tree growth along elevational gradients. Tree cover beneath this limit forms an ecotone with diverse spatial configurations. However, global-scale quantification of these ecotone patterns and their underlying environmental drivers remains lacking. We used very-high-resolution satellite imagery and landscape metrics to characterize fine-scale treeline-ecotone spatial patterns globally. The variations in tree-cover distributions within the ecotones were effectively described by the leading principal components from landscape metrics, which captured the level of tree-cover aggregation into patches and patch complexity. Highly patchy ecotones, where trees grow individually, are most common where snow, wind, topographic relief, and nontree vegetation cover are high, occurring in areas where the upper tree limits approach the thermal limits to tree growth. Upper tree limits located far below the thermal limits tend to exhibit discrete ecotones. Among the treeline tree genera, Pinus stood out as forming patchier and Nothofagus as forming more discrete ecotones. We show that alpine treeline ecotones follow predictable global spatial patterns, allowing the formulation of hypotheses about the processes controlling pattern formation and ecotone dynamics. With the presented method to describe fine-scale patterns globally, we gain a powerful indicator for predicting forest expansion under climate change.
The effects of elevated CO2 (eCO2) on tree growth and carbon dynamics may be constrained by soil phosphorus (P) availability. However, whether their interaction shapes the fate of recent photosynthetic carbon allocation along plant-soil-microbe compartments is rarely explored. Potted Pinus massoniana seedlings were grown under two levels of CO2 (aCO2: 420 ppm and eCO2: 800 ppm) and four P treatments (0, 25, 50, and 100 kg P ha-1 yr-1) in Open-Top Chambers, with 13C labeling employed to trace allocation of recent carbon among plant organs, soil, and microbes. Biomass, structural, and non-structural carbohydrates were also determined. Results showed that eCO2 increased the allocation of 13C to the root, while eCO2 + P100 prioritized allocation to the leaf. eCO2 consistently raised DO13C (13C-dissolved organic carbon), but its effect on MB13C (13C-microbial biomass carbon) was significant only at P50 and P100. Correlation analysis confirmed the carbon flow from leaf to stem to root and identified root 13C as the key source for dissolved organic carbon and a critical driver for microbial carbon buildup under sufficient P. Our findings indicate that P addition modulated 13C allocation among plant organs under eCO2 and enabled microbes to efficiently utilize root-derived carbon, demonstrating that P availability serves as a key regulator of carbon-phosphorus exchange in the plant-soil-microbe system of P. massoniana.
Drought stress constrains the productivity of terrestrial ecosystems and the distribution of plant species. To withstand drought stress, plants have evolved diverse water-use strategies. Despite the critical function of roots in whole-plant water regulation, drought strategies have been primarily studied from an aboveground perspective, and so our knowledge of how fine-root traits are related to aboveground hydraulic traits remains limited. Here, we compiled a dataset of primarily woody species comprising five aboveground plant hydraulic traits associated with water-use strategies and four fine-root traits from the root economics space (RES). We investigated how the global diversity in ecological strategies of the RES traits relates to aboveground hydraulic traits contributing to drought resistance. We found a slight trend towards acquisitive species with higher root nitrogen content and lower root tissue density having lower drought resistance in aboveground tissues. Species with thicker roots displayed a tendency towards slightly higher drought resistance than thin-rooted species. The weakness of these relationships suggests that aboveground drought adaptations are largely independent of classical axes of fine root ecological strategies, pointing to either a decoupling between aboveground and belowground responses or a stronger coordinating role for other root traits such as maximum rooting depth or root cortex fraction in hydraulic adaptation.
The evolutionary arms race between plants and herbivores led to numerous plant adaptations, including spinescence. However, the balance between herbivory and abiotic conditions in the evolution of spinescence remains unclear. We integrated phylogenetic, geographic, and trait data for 2686 species of an ecologically diverse and spinescent pantropical lineage, mimosoid legumes, with distribution data on 368 extant and extinct mammalian herbivores ≥ 10 kg. Using structural equation models, we assessed how herbivores, climate, soil, and fire directly and indirectly affected the proportion of spinescent mimosoids across global and continental assemblages. Models incorporating extinct herbivore assemblages explained more variation in the proportion of spiny species than those based solely on extant herbivores. Dry-season length and soil pH increased spinescence both directly and indirectly through their effects on herbivore richness. These abiotic effects exceeded herbivore effects at continental scales. Fire influenced spinescence only indirectly via its positive relationship with herbivore richness. Finally, spinescence evolved repeatedly across mimosoids from c. 35 million years ago, pre-dating the Miocene savanna expansion. Our study suggests that past herbivore communities have left a lasting imprint on present-day plant defence patterns and that long-term climatic transitions and the emergence of open, herbivore-rich landscapes played crucial roles in the evolution and distribution of spinescence.
Remotely sensed measurements of equivalent water thickness (EWT) derived from visible-shortwave infrared imaging spectroscopy data have the potential to revolutionize how we monitor drought in natural ecosystems. However, the mechanistic underpinnings of EWT measurements are still relatively unknown. We collected coincident measurements of leaf spectra, leaf water content, and leaf water potential over the course of a tabletop leaf drydown for 13 tree species. We then used a vegetation radiative transfer model to scale these measurements from the leaf to canopy scale, simulating how a leaf drying event would appear from an airborne or satellite instrument. We found that EWT responses to changes in leaf water content are strongly species-specific at both the leaf and canopy level. Furthermore, changes in EWT associated with declining leaf water are relatively small compared to those associated with potential canopy structural changes, such as leaf shedding or shifting leaf angle distribution, and with retrieval errors of current instruments. Our results suggest that single point-based EWT measurements are unlikely to reliably detect drought stress across species due to several confounding factors, but that time series data (newly available through operational and upcoming spaceborne imaging spectrometers) may enable approaches that circumvent many of these challenges.
The vast majority of land plants transfer part of the organic carbon they produce by photosynthesis to arbuscular mycorrhizal (AM) fungi inside their root cells; the fungi in turn help plants to take up nutrients and water from the soil. This carbon can subsequently be acquired from mycorrhizal fungi by rare nonphotosynthetic 'mycoheterotrophic' plants that tap into the same fungal network. However, recent findings suggest that carbon uptake from AM fungi may exist among some green plants too. If so, this would qualify them as partial mycoheterotrophs (mixotrophs) rather than as pure autotrophs. Here, we discuss the evolutionary, ecophysiological, morphological, genetic, and environmental evidence for the existence and prevalence of this trait. We conclude that there is strong, albeit indirect, evidence for its existence, although its taxonomic distribution remains to be determined. This knowledge gap currently prevents us from inferring the magnitude of AM partial mycoheterotrophy in terrestrial ecosystems, which in turn severely limits our understanding of its role in plant establishment and survival and in ecosystem structure and function.