Regulation of Axillary Meristem Initiation by Transcription Factors and Plant Hormones

Abstract

One distinctive feature of plant post-embryonic development is that plants can undergo reiterative growth and continuous organogenesis throughout their lifetimes. Axillary meristems (AMs) in leaf axils play a central role in this growth and differences in meristem initiation and development produce the diversity of plant architecture. Studies in the past 15 years have shown that several transcription factors (TFs) and phytohormones affect AM initiation. In this review, we highlight recent research using systems biology approaches to examine the regulatory hierarchies underlying AM initiation and the role of auxins and cytokinins in AM initiation and development. This research revealed a developmental mechanism in which phytohormone signals act with a gene regulatory network containing multiple TFs to contribute to the initiation of AMs.

Cytokinin Signaling Activates WUSCHEL Expression during Axillary Meristem Initiation

“…The activity of the AM determines plant architecture and crop yield (McSteen and Leyser, 2005;Wang and Li, 2008;Yang and Jiao, 2016). The finding that cytokinin activates WUS expression provides insight into how shoot stem cell niches are established and may ultimately facilitate the manipulation of plant architecture to enhance crop yield.…”

Corner's rules as a framework for plant morphology, architecture and functioning – issues and steps forward

“…(b, c) leptocaul beech tree, Fagus sylvatica ); and (d) relationships that determine the correlation space between stem and appendages are initiated in the shoot apical meristem ( SAM ) where cell number positively affects meristem size which, in turn, positively affects stem diameter and leaf area (blue arrows; Schnablová et al ., ). The axillary meristem, which is initiated in the boundary regions between the adaxial base of the leaf primordium and the SAM , is closely associated with leaf polarity and also results from signals from the SAM (yellow arrows; Yang & Jiao, ; Chomicki et al ., ). To what extent leaf and stem size and shape, and axillary production size and fate, are pre‐determined in the SAM or result from later interactions among growing organs needs to be further investigated.…”

“…Furthermore, axillary meristem initiation from which a branch or an inflorescence develops is tightly related to the boundary regions between the SAM and the leaf primordium (yellow arrows in Fig. d; Yang & Jiao, ) suggesting that the growth, and likely fate of the axillary production, is not passive but partly determined by interactions between the SAM and newly initiated organs at a very early stage. This is supported by findings on branch plagiotropy in Araucaria and Coffea likely resulting from an early SAM signal (see discussion in Chomicki et al ., ).…”

Gibberellin repression of axillary bud formation in Arabidopsis by modulation of DELLA‐SPL9 complex activity

“…Studies over the past decades have indicated that many transcription factors (TFs) and phytohormones affect the initiation of AMs. Most of the known genes that affect AMs initiation encode TFs, such as SHOOT MERISTEMLESS (STM), LATERAL SUPPRESSOR (LAS), REVOLUTA (REV), REGULATOR OF AXILLARY MERISTEMS (RAX), TILLERS ABSENT1 (TAB1, also known as OsWUS), MONOCULM1 (MOC1) and NAC domain proteins CUC1, CUC2 and CUC3 (Otsuga et al ; Greb et al ; Li et al ; Hibara et al ; Keller et al ; Müller et al ; Tanaka et al ; Yang and Jiao ). Genetics research and genome scale analysis have revealed the potential gene regulatory network (GRN) of AMs initiation.…”