Department of Plant Sciences, University of Cambridge, Cambridge, UK.
Plant Cell Environ. 2024 Jul;47(7):2597-2613. doi: 10.1111/pce.14902. Epub 2024 Mar 28.
Plant leaves contain multiple cell types which achieve distinct characteristics whilst still coordinating development within the leaf. The bundle sheath possesses larger individual cells and lower chloroplast content than the adjacent mesophyll, but how this morphology is achieved remains unknown. To identify regulatory mechanisms determining bundle sheath cell morphology we tested the effects of perturbing environmental (light) and endogenous signals (hormones) during leaf development of Oryza sativa (rice). Total chloroplast area in bundle sheath cells was found to increase with cell size as in the mesophyll but did not maintain a 'set-point' relationship, with the longest bundle sheath cells demonstrating the lowest chloroplast content. Application of exogenous cytokinin and gibberellin significantly altered the relationship between cell size and chloroplast biosynthesis in the bundle sheath, increasing chloroplast content of the longest cells. Delayed exposure to light reduced the mean length of bundle sheath cells but increased corresponding leaf length, whereas premature light reduced final leaf length but did not affect bundle sheath cells. This suggests that the plant hormones cytokinin and gibberellin are regulators of the bundle sheath cell-chloroplast relationship and that final bundle sheath length may potentially be affected by light-mediated control of exit from the cell cycle.
植物叶片包含多种细胞类型，这些细胞在协调叶片发育的同时具有不同的特征。与相邻的叶肉相比，维管束鞘具有更大的单个细胞和更低的叶绿体含量，但这种形态是如何形成的仍不清楚。为了确定决定维管束鞘细胞形态的调控机制，我们在水稻叶片发育过程中测试了干扰环境（光）和内源性信号（激素）的影响。维管束鞘细胞中的总叶绿体面积随着细胞尺寸的增加而增加，与叶肉中的情况相同，但没有维持“设定点”关系，最长的维管束鞘细胞表现出最低的叶绿体含量。外源细胞分裂素和赤霉素的应用显著改变了维管束鞘中细胞大小和叶绿体生物合成之间的关系，增加了最长细胞的叶绿体含量。延迟光照暴露会降低维管束鞘细胞的平均长度，但会增加相应的叶片长度，而过早光照会降低最终叶片长度，但不会影响维管束鞘细胞。这表明植物激素细胞分裂素和赤霉素是维管束鞘细胞-叶绿体关系的调节剂，并且最终维管束鞘长度可能会受到光介导的细胞周期退出控制的影响。
