Abstract
SummaryIn Arabidopsis, the miR171‐GRAS module has been clarified as key player in meristem maintenance. However, the knowledge about its role in fruit crops like tomato (Solanum lycopersicum) remains scarce. We previously identified tomato SlGRAS24 as a target gene of Sly‐miR171. To study the role of this probable transcription factor, we generated transgenic tomato plants underexpressing SlGRAS24, overexpressing SlGRAS24, overexpressing Sly‐miR171 and expressing β‐glucuronidase (GUS) under the SlGRAS24 promoter (proSlGRAS24‐GUS). Plants overexpressing SlGRAS24 (SlGRAS24‐OE) had pleiotropic phenotypes associated with multiple agronomical traits including plant height, flowering time, leaf architecture, lateral branch number, root length, fruit set and development. Many GA/auxin‐related genes were down‐regulated and altered responsiveness to exogenous IAA/NAA or GA 3 application was observed in SlGRAS24‐OE seedlings. Moreover, compromised fruit set and development in SlGRAS24‐OE was also observed. These newly identified phenotypes for SlGRAS24 homologs in tomato were later proved to be caused by impaired pollen sacs and fewer viable pollen grains. At anthesis, the comparative transcriptome results showed altered expression of genes involved in pollen development and hormone signalling. Taken together, our data demonstrate that SlGRAS24 participates in a series of developmental processes through modulating gibberellin and auxin signalling, which sheds new light on the involvement of hormone crosstalk in tomato development.
Highlights
The GRAS family of plant proteins is responsible for regulating many aspects of growth, development and responses to the biotic and abiotic environment
SlGRAS24 is phylogenetically clustered into the HAIRY MERISTEM (HAM) subfamily of GRAS genes and shows the highest sequence identity with Arabidopsis thaliana AtSCL6 (Huang et al, 2015)
We hypothesized that the SlGRAS24 gene and its regulator SlymiR171 would have similar functions in tomato as their respective orthologs in Arabidopsis (Wang et al, 2010)
Summary
The GRAS family of plant proteins is responsible for regulating many aspects of growth, development and responses to the biotic and abiotic environment. It is found that HAM proteins act as conserved interacting cofactors with WUS/WOX proteins They share common targets and their physical interaction is important in driving downstream transcriptional programmes and in promoting shoot stem cell proliferation (Zhou et al, 2015). MiR171-GRAS module controls flowering time (phase transition) and trichome distribution via inhibiting the activity of miR156-targeted SPL proteins (Xue et al, 2014) This module is critical for mediating GA-DELLA signalling in the coordinate regulation of chlorophyll biosynthesis and leaf growth in light (Ma et al, 2014). It has been extensively studied about the role of miR171 upon various stresses in different species, including Arabidopsis, barley, maize and Solanum tuberosum (Hwang et al, 2011; Kantar et al, 2010; Kong et al, 2010; Liu et al, 2008)
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