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

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.

Induction and Characterization of Tetraploid Through Zygotic Chromosome Doubling in Eucalyptus urophylla

“…After polyploidization, the expression of genes related to chlorophyll synthesis in Arabidopsis thaliana and Chrysanthemum nankingense was upregulated, resulting in enhanced photosynthesis ( Ni et al, 2009 ; Dong et al, 2017 ). The upregulated expression of GRF5 in Populus polyploids leads to its production of leaves with a larger leaf area ( Wu et al, 2021 ). Exploring the differences in gene expression after plant polyploidization is of great significance for analyzing the variation of polyploid traits ( Du et al, 2020 ).…”

“…However, the cell volume increased after tetraploidy in E. urophylla ( Figures 4D , 6F ). The upregulated expression of GRF5 can increase cell volume ( Wu et al, 2021 ), and the expression of GRF5 in both young and mature tetraploid leaves was significantly higher than that in diploid leaves, which may cause the enlargement of cell volume. The increase in cell number and volume can remarkably increase plant organ size, which also suggests that changes in plant organs after polyploidy are caused by multiple gene expression changes.…”

The diverse roles of cytokinins in regulating leaf development

“…In poplar, GRF5-1 can bind to the promoter of CKX1 and inhibit its expression. The cytokinin concentration in the apical buds and immature leaves of GRF5-1 -overexpressing transgenic plants increased, which increased the number of mesophyll cells and leaf area 122 . In brief, during the leaf cell proliferation stage, cytokinins increase the number of leaf cells by promoting the mitotic replication cycle and accelerating cell division in different facets, thereby regulating leaf size.…”

Genome-Wide Identification and Analysis of the Growth-Regulating Factor Family in Zanthoxylum armatum DC and Functional Analysis of ZaGRF6 in Leaf Size and Longevity Regulation

“…GRFs generally play positive roles in plant growth and development. Studies have shown that overexpression of GRFs leads to increase cell proliferation and leaf expansion in rice, Arabidopsis , poplar, and lettuce [ 10 , 21 , 29 , 30 , 31 ]. However, GRF genes have been reported to play negative roles in plant growth as well.…”