The reduction in maize leaf growth under mild drought affects the transition between cell division and cell expansion and cannot be restored by elevated gibberellic acid levels.

Hilde Nelissen,Rafael Abbeloos,Mikko Kojima,Frederik Coppens,Xiao‐Huan Sun,Yumiko Takebayashi,Veronique Storme,Jolien De Block,Steven Maere,Dirk Inzé,Yusuke Jikumaru,Dorota Herman,Marnik Vuylsteke,Hitoshi Sakakibara,Bart Rymen,Gerrit T.S Beemster,Yuji Kamiya,Kirin Demuynck

doi:10.1111/pbi.12801

Abstract

SummaryGrowth is characterized by the interplay between cell division and cell expansion, two processes that occur separated along the growth zone at the maize leaf. To gain further insight into the transition between cell division and cell expansion, conditions were investigated in which the position of this transition zone was positively or negatively affected. High levels of gibberellic acid (GA) in plants overexpressing the GA biosynthesis gene GA20‐OXIDASE (GA20OX‐1 OE) shifted the transition zone more distally, whereas mild drought, which is associated with lowered GA biosynthesis, resulted in a more basal positioning. However, the increased levels of GA in the GA20OX‐1 OE line were insufficient to convey tolerance to the mild drought treatment, indicating that another mechanism in addition to lowered GA levels is restricting growth during drought. Transcriptome analysis with high spatial resolution indicated that mild drought specifically induces a reprogramming of transcriptional regulation in the division zone. ‘Leaf Growth Viewer’ was developed as an online searchable tool containing the high‐resolution data.

Highlights

Plants are continuously producing organs that grow to fulfil specific roles during plant development, and the sessile nature of plants urges them to adjust their growth when the environment changes
The processes of cell division and cell expansion are mainly viewed as spatially and/or temporally regulated (Gonzalez et al, 2012; Nelissen et al, 2012; Sozzani and Iyer-Pascuzzi, 2014), and it becomes increasingly clear that the regulation of the growth mechanisms in dicot and monocot leaves is to a great extend conserved (Nelissen et al, 2016)
We investigated the effect of mild drought on this transition zone between cell division and cell expansion in B104, an inbred that is closely related to B73 (Liu et al, 2003) and that can be routinely transformed (Coussens et al, 2012; Frame et al, 2006)

Summary

Introduction

Plants are continuously producing organs that grow to fulfil specific roles during plant development, and the sessile nature of plants urges them to adjust their growth when the environment changes. The processes of cell division and cell expansion are mainly viewed as spatially and/or temporally regulated (Gonzalez et al, 2012; Nelissen et al, 2012; Sozzani and Iyer-Pascuzzi, 2014), and it becomes increasingly clear that the regulation of the growth mechanisms in dicot and monocot leaves is to a great extend conserved (Nelissen et al, 2016) One of these conserved mechanisms that represents an important developmental switch is the transition from cell division to cell expansion, for which already a large number of genes and molecular pathways have been identified (Breuninger and Lenhard, 2010; Gonzalez et al, 2012; Nelissen et al, 2012; Sozzani and Iyer-Pascuzzi, 2014). Differences in the cell cycle arrest front have been observed in genetic (Mizukami and Fischer, 2000; Nath et al, 2003; Vercruyssen et al, 2014) and environmental (Skirycz et al, 2011) perturbations

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