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Abstract
Plant shoot systems derive from the shoot apical meristems (SAMs), pools of stems cells that are regulated by a feedback between the WUSCHEL (WUS) homeobox protein and CLAVATA (CLV) peptides and receptors. The maize heterotrimeric G protein α subunit COMPACT PLANT2 (CT2) functions with CLV receptors to regulate meristem development. In addition to the sole canonical Gα CT2, maize also contains three eXtra Large GTP-binding proteins (XLGs), which have a domain with homology to Gα as well as additional domains. By either forcing CT2 to be constitutively active, or by depleting XLGs using CRISPR-Cas9, here we show that both CT2 and XLGs play important roles in maize meristem regulation, and their manipulation improved agronomic traits. For example, we show that expression of a constitutively active CT2 resulted in higher spikelet density and kernel row number, larger ear inflorescence meristems (IMs) and more upright leaves, all beneficial traits selected during maize improvement. Our findings suggest that both the canonical Gα, CT2 and the non-canonical XLGs play important roles in maize meristem regulation and further demonstrate that weak alleles of plant stem cell regulatory genes have the capacity to improve agronomic traits.
Highlights
The plant shoot system is derived from the shoot apical meristems (SAMs), pools of stems cells that have the ability of self-renewal, while initiating new leaves and axillary meristems [1]
We demonstrate that COMPACT PLANT2 (CT2) and XLGs have both redundant and specialized functions in regulating shoot development
We demonstrate that CT2 and XLGs have both redundant and specialized functions in regulating meristem development, and importantly, manipulation of maize Gα subunits introduced desirable agronomic traits
Summary
The plant shoot system is derived from the SAMs, pools of stems cells that have the ability of self-renewal, while initiating new leaves and axillary meristems [1]. The CLV-WUS negative feedback loop has been identified as the key pathway to regulate SAM proliferation and differentiation in Arabidopsis, and is widely conserved in other species [2]. This pathway relies on the communication between a battery of receptors, peptides and transcription factors. WUS, a homeodomain transcription factor expressed in the organizing center, promotes stem cell fate [2], while CLV3, a small peptide ligand that is secreted from stem cells at the tip of the SAM, is perceived by leucine-rich repeat (LRR) receptor kinases, such as CLV1, and receptor-like protein CLV2, resulting in the repression of WUS transcription [3,4,5]. The signaling players and mechanisms downstream of the CLV receptors are poorly understood
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