Gravity sensing in plants.

内容摘要

Gravity, a constant force on Earth, fundamentally shapes plant architecture by directing organ growth, a process known as gravitropism. Shoots typically grow upward (negative gravitropism) and roots downward (positive gravitropism). In seed plants, gravity is sensed by specialized cells, including endodermal cells in shoots and columella cells in roots, collectively termed statocytes. The gravitropic response occurs through three sequential steps: gravity sensing/perception, signal transduction, and growth response. For over a century, the starch-statolith hypothesis dominated our conceptual understanding of gravity sensing, yet its molecular mechanism remained elusive. A molecular basis was established in 2023, when sedimenting amyloplasts were shown to repolarize LAZY proteins. This discovery allows us to molecularly define one type of gravity sensing as the process from amyloplast sedimentation (physical susception) to LAZY repolarization (physiological signal conversion). Meanwhile, evidence suggests the existence of alternative gravity-sensing pathways independent of the starch-statolith model, the mechanisms of which remain largely unknown. This review summarizes current knowledge and perspectives on gravity sensing, primarily in vascular plants, while integrating key insights from nonvascular lineages to provide an evolutionary context. Potential agricultural applications of gravity-sensing mechanisms are also discussed. 重力是地球上恒定存在的力，通过指引器官的生长方向从根本上塑造了植物的形态结构。植物对重力刺激产生定向生长反应的过程被称为向重力性。植物的地上部分通常表现为向上生长(负向重力性)，而根则向下生长(正向重力性)。在种子植物中，重力由特化的细胞所感知，包括茎中的内皮层细胞和根中的根冠柱细胞，它们统称为平衡细胞。向重力性反应通过三个连续步骤完成:重力感受、信号转导和生长反应。一个多世纪以来，“淀粉‐平衡石”假说主导着我们对重力感受的认知，但其分子机制一直未被揭示。2023年，淀粉体沉降被证明可使LAZY蛋白重新极性化，从而为这一机制奠定了分子基础。这一发现使我们能够从分子层面将一类重力感受定义为从淀粉体沉降(物理感知)到LAZY蛋白重新极性化(生理信号转换)的过程。同时，有证据表明存在不依赖于“淀粉‐平衡石”模型的其他重力感受通路，但其机制在很大程度上仍不清楚。本文综述了当前关于重力感受的研究进展与观点，主要以维管植物为对象，同时从演化视角整合了非维管植物的关键发现，并探讨了重力感受机制潜在的农业应用价值。.