Plant Developmental Biology Group, Wageningen University Research, 6708 PB Wageningen, The Netherlands.
Plant Developmental Biology Group, Wageningen University Research, 6708 PB Wageningen, The Netherlands
Proc Natl Acad Sci U S A. 2017 Oct 31;114(44):11709-11714. doi: 10.1073/pnas.1714410114. Epub 2017 Oct 16.
Plant development is characterized by repeated initiation of meristems, regions of dividing cells that give rise to new organs. During lateral root (LR) formation, new LR meristems are specified to support the outgrowth of LRs along a new axis. The determination of the sequential events required to form this new growth axis has been hampered by redundant activities of key transcription factors. Here, we characterize the effects of three PLETHORA (PLT) transcription factors, PLT3, PLT5, and PLT7, during LR outgrowth. In triple mutants, the morphology of lateral root primordia (LRP), the auxin response gradient, and the expression of meristem/tissue identity markers are impaired from the "symmetry-breaking" periclinal cell divisions during the transition between stage I and stage II, wherein cells first acquire different identities in the proximodistal and radial axes. Particularly, , , and genes that are typically expressed later than , , and during LR outgrowth are not induced in the mutant primordia, rendering "PLT-null" LRP. Reintroduction of any PLT clade member in the mutant primordia completely restores layer identities at stage II and rescues mutant defects in meristem and tissue establishment. Therefore, all genes can activate the formative cell divisions that lead to de novo meristem establishment and tissue patterning associated with a new growth axis.
植物发育的特征是反复启动分生组织，即产生新器官的分裂细胞区域。在侧根 (LR) 形成过程中，新的 LR 分生组织被指定以支持 LR 沿着新轴的生长。由于关键转录因子的冗余活性，形成这个新生长轴的顺序事件的确定受到了阻碍。在这里，我们描述了三个 PLETHORA (PLT) 转录因子 PLT3、PLT5 和 PLT7 在 LR 生长过程中的作用。在三突变体中，侧根原基 (LRP) 的形态、生长素响应梯度以及分生组织/组织身份标记物的表达在 I 期和 II 期之间的“对称性破坏”平周细胞分裂中受到损害，在此期间，细胞首先在近-远轴和辐射轴上获得不同的身份。特别是，在 LR 生长过程中表达晚于 、 、 和 的 、 、 和 基因在突变原基中没有被诱导，导致“PLT 缺失”LRP。在突变原基中重新引入任何 PLT 类群成员完全恢复了 II 期的层身份，并挽救了突变体在分生组织和组织建立中的缺陷。因此，所有 基因都可以激活导致新分生组织建立和与新生长轴相关的组织模式形成的有形成分的细胞分裂。
