Growth‐regulating factor 5 (GRF5)‐mediated gene regulatory network promotes leaf growth and expansion in poplar

Wenqi Wu,Jiang Li,Hairong Wei,Xiangyang Kang,Kaiwen Lv,Kang Du,Wenli Zhang,Quanzi Li,Qiao Wang

doi:10.1111/nph.17179

Abstract

Summary Although polyploid plants have larger leaves than their diploid counterparts, the molecular mechanisms underlying this difference (or trait) remain elusive.Differentially expressed genes (DEGs) between triploid and full‐sib diploid poplar trees were identified from two transcriptomic data sets followed by a gene association study among DEGs to identify key leaf growth regulators. Yeast one‐hybrid system, electrophoretic mobility shift assay, and dual‐luciferase assay were employed to substantiate that PpnGRF5‐1 directly regulated PpnCKX1. The interactions between PpnGRF5‐1 and growth‐regulating factor (GRF)‐interacting factors (GIFs) were experimentally validated and a multilayered hierarchical regulatory network (ML‐hGRN)‐mediated by PpnGRF5‐1 was constructed with top‐down graphic Gaussian model (GGM) algorithm by combining RNA‐sequencing data from its overexpression lines and DAP‐sequencing data.PpnGRF5‐1 is a negative regulator of PpnCKX1. Overexpression of PpnGRF5‐1 in diploid transgenic lines resulted in larger leaves resembling those of triploids, and significantly increased zeatin and isopentenyladenine in the apical buds and third leaves. PpnGRF5‐1 also interacted with GIFs to increase its regulatory diversity and capacity. An ML‐hGRN‐mediated by PpnGRF5‐1 was obtained and could largely elucidate larger leaves.PpnGRF5‐1 and the ML‐hGRN‐mediated by PpnGRF5‐1 were underlying the leaf growth and development.

Highlights

The majority (75%) of polyploids are allopolyploids (Grant, 1981; Brochmann et al, 2004)
Since it is not clear whether cell division, cell expansion, or both contribute to faster leaf growth in triploids, we studied the paradermal view of palisade cells in at least eight samples of the fifth leaf blades from apical buds
Overexpression of PpnGRF5-1 in 84k diploid poplar led to larger leaves that resembled those of triploids, indicating that PpnGRF5-1 and its downstream target genes are sufficient to drive leaf growth and produce triploid leaf phenotypes

Summary

Introduction

The majority (75%) of polyploids are allopolyploids (Grant, 1981; Brochmann et al, 2004). Recent studies on several species have shown that the growth advantage of leaves in polyploids is more salient than any other trait, for example, poplar triploids (Liao et al, 2016) and tetraploids (Xu et al, 2016), birch tetraploids (Mu et al, 2012), Eucommia ulmoides triploids (Li et al, 2019) and tetraploids (Tokumoto et al, 2016) and Eucalyptus triploids (Yang et al, 2018) and tetraploids (Fernando et al, 2019) The fact that both triploids and tetraploids display much larger leaves than their comparable (e.g. full-sib) diploids implies that the ploidy is the primary cause of bigger leaf areas in polyploids. In Arabidopsis thaliana, both leaf area and cell size in tetraploids are consistently larger than diploids (Ni et al, 2009)

Methods

Results

Discussion

Conclusion