Woerlen Natalie, Allam Gamalat, Popescu Adina, Corrigan Laura, Pautot Véronique, Hepworth Shelley R
Department of Biology and Institute of Biochemistry, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada.
Institut Jean-Pierre Bourgin, UMR1318, INRA, Agro Paris Tech, CNRS, Université Paris-Saclay, RD10, 78026, Versailles Cedex, France.
Planta. 2017 Jun;245(6):1079-1090. doi: 10.1007/s00425-017-2663-2. Epub 2017 Feb 15.
Repression of boundary genes by KNOTTED1-like homeodomain transcription factor BREVIPEDICELLUS promotes the differentiation of phase II secondary xylem in Arabidopsis roots. Plant growth and development relies on the activity of meristems. Boundaries are domains of restricted growth that separate forming organs and the meristem. Class I KNOX homeodomain transcription factors are important regulators of meristem maintenance. Members of this class including BREVIDICELLUS also called KNOTTED-LIKE FROM ARABIDOPSIS THALIANA1 (BP/KNAT1) fulfill this function in part by spatially regulating boundary genes. The vascular cambium is a lateral meristem that allows for radial expansion of organs during secondary growth. We show here that BP/KNAT1 repression of boundary genes plays a crucial role in root secondary growth. In particular, exclusion of BLADE-ON-PETIOLE1/2 (BOP1/2) and other members of this module from xylem is required for the differentiation of lignified fibers and vessels during the xylem expansion phase of root thickening. These data reveal a previously undiscovered role for boundary genes in the root and shed light on mechanisms controlling wood development in trees.
类KNOTTED1同源异型域转录因子BREVIPEDICELLUS对边界基因的抑制促进了拟南芥根中II期次生木质部的分化。植物的生长和发育依赖于分生组织的活性。边界是限制生长的区域，将正在形成的器官与分生组织分隔开来。I类KNOX同源异型域转录因子是分生组织维持的重要调节因子。包括BREVIDICELLUS（也称为拟南芥KNOTTED-LIKE1，BP/KNAT1）在内的该类成员部分通过空间调节边界基因来履行这一功能。维管形成层是一种侧生分生组织，在次生生长过程中允许器官进行径向扩展。我们在此表明，BP/KNAT1对边界基因的抑制在根的次生生长中起关键作用。特别是，在根增粗的木质部扩展阶段，将叶柄上的叶片1/2（BOP1/2）和该模块的其他成员排除在木质部之外，是木质化纤维和导管分化所必需的。这些数据揭示了边界基因在根中以前未被发现的作用，并阐明了树木木材发育的控制机制。
