Overexpression of the Transcription Factors GmSHN1 and GmSHN9 Differentially Regulates Wax and Cutin Biosynthesis, Alters Cuticle Properties, and Changes Leaf Phenotypes in Arabidopsis.

Yangyang Xu,Hanying Wu,Mingming Zhao,Yinong Xu,Dan Gu,Wang Wu

doi:10.3390/ijms17040587

Abstract

SHINE (SHN/WIN) clade proteins, transcription factors of the plant-specific APETALA 2/ethylene-responsive element binding factor (AP2/ERF) family, have been proven to be involved in wax and cutin biosynthesis. Glycine max is an important economic crop, but its molecular mechanism of wax biosynthesis is rarely characterized. In this study, 10 homologs of Arabidopsis SHN genes were identified from soybean. These homologs were different in gene structures and organ expression patterns. Constitutive expression of each of the soybean SHN genes in Arabidopsis led to different leaf phenotypes, as well as different levels of glossiness on leaf surfaces. Overexpression of GmSHN1 and GmSHN9 in Arabidopsis exhibited 7.8-fold and 9.9-fold up-regulation of leaf cuticle wax productions, respectively. C31 and C29 alkanes contributed most to the increased wax contents. Total cutin contents of leaves were increased 11.4-fold in GmSHN1 overexpressors and 5.7-fold in GmSHN9 overexpressors, mainly through increasing C16:0 di-OH and dioic acids. GmSHN1 and GmSHN9 also altered leaf cuticle membrane ultrastructure and increased water loss rate in transgenic Arabidopsis plants. Transcript levels of many wax and cutin biosynthesis and leaf development related genes were altered in GmSHN1 and GmSHN9 overexpressors. Overall, these results suggest that GmSHN1 and GmSHN9 may differentially regulate the leaf development process as well as wax and cutin biosynthesis.

Highlights

Higher plants have developed an extracellular hydrophobic cuticle layer that covers their aerial epidermis, providing protection against nonstomatal water loss and various forms of biotic and abiotic stresses [1,2,3,4]
Wax biosynthesis begins at the endoplasmic reticulum (ER) with C16 and C18 fatty acids as precursors, followed by the fatty acid elongation process through which fatty acids are converted into very-long-chain fatty acids (VLCFAs)
Soybean SHN proteins share two other conserved motifs, middle motif and C-terminal motif, with Arabidopsis SHN clade members. Genes encoding these homologs in soybean were designated as GmSHN1 to GmSHN10 based on amino acid sequence similarity score to AtSHN1: GmSHN1 (Glyma07g03500), GmSHN2 (Glyma08g22590), GmSHN3 (Glyma13g23570), GmSHN4 (Glyma17g12330), GmSHN5 (Glyma15g01140), GmSHN6 (Glyma06g29110), GmSHN7 (Glyma04g19650), GmSHN8 (Glyma06g07240), GmSHN9 (Glyma17g31900) and GmSHN10

Summary

Introduction

Higher plants have developed an extracellular hydrophobic cuticle layer that covers their aerial epidermis, providing protection against nonstomatal water loss and various forms of biotic and abiotic stresses [1,2,3,4]. Cuticle is a heterogeneous layer consists of cutin polyester matrix covered with epicuticular waxes and filled with intracuticular waxes [5,6]. Mainly composed of very-long-chain alkanes, fatty acids, primary and secondary alcohols, esters, aldehydes, and ketones, are responsible for the glossy appearances in leaves and fruits [7]. Wax biosynthesis begins at the endoplasmic reticulum (ER) with C16 and C18 fatty acids as precursors, followed by the fatty acid elongation process through which fatty acids are converted into very-long-chain fatty acids (VLCFAs). One is the alkane forming pathway that yields aldehydes, alkanes, secondary alcohols, and ketones; the other one is the alcohol forming pathway that produces primary alcohols and esters [8]

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Conclusion