Plant organ size control: AINTEGUMENTA regulates growth and cell numbers during organogenesis

The control of cell proliferation during organogenesis plays an important role in initiation, growth, and acquisition of the intrinsic size of organs in higher plants. To understand the developmental mechanism that controls intrinsic organ size by regulating the number and extent of cell division during organogenesis, we examined the function of the Arabidopsis regulatory gene AINTEGUMENATA (ANT). Previous observations revealed that ANT regulates cell division in integuments during ovule development and is necessary for floral organ growth. Here we show that ANT controls plant organ cell number and organ size throughout shoot development. Loss of ANT function reduces the size of all lateral shoot organs by decreasing cell number. Conversely, gain of ANT function, via ectopic expression of a 35S::ANT transgene, enlarges embryonic and all shoot organs without altering superficial morphology by increasing cell number in both Arabidopsis and tobacco plants. This hyperplasia results from an extended period of cell proliferation and organ growth. Furthermore, cells ectopically expressing ANT in fully differentiated organs exhibit neoplastic activity by producing calli and adventitious roots and shoots. Based on these results, we propose that ANT regulates cell proliferation and organ growth by maintaining the meristematic competence of cells during organogenesis.

器官发生过程中的细胞增殖调控，对高等植物器官的起始、生长及固有尺寸的建成具有关键作用。为解析通过调控器官发生过程中的细胞分裂数目与范围，进而控制器官固有尺寸的发育机制，本研究针对拟南芥调控基因AINTEGUMENATA（ANT）的功能展开了探究。既往研究显示，ANT在胚珠发育过程中调控珠被的细胞分裂，且为花器官的正常生长所必需。本研究证实，ANT可在整个茎发育阶段调控植物器官的细胞数目与器官尺寸。ANT功能缺失会通过降低细胞数目，导致所有侧生茎器官的尺寸缩小。与之相反，通过异位表达35S::ANT转基因，可增强ANT的功能，在不改变器官表面形态的前提下，通过增加细胞数目，使拟南芥与烟草的胚胎及所有茎器官的尺寸增大。这种细胞增生现象源于细胞增殖与器官生长时期的延长。此外，在完全分化的器官中异位表达ANT的细胞，可通过产生愈伤组织、不定根与不定芽，表现出赘生性活性。基于上述研究结果，我们提出：ANT可通过维持器官发生过程中细胞的分生组织潜能，调控细胞增殖与器官生长。