Three Transcription Activators of ABA Signaling Positively Regulate Suberin Monomer Synthesis by Activating Cytochrome P450 CYP86A1 in Kiwifruit.

Xiaopeng Wei,Yajie Yang,Weiliang Guan,Linchun Mao,Xueyuan Han,Xiaobo Wei,Wenjing Lu,Changjie Xu,Zisheng Luo,Meng Zha

doi:10.3389/fpls.2019.01650

Abstract

Wound attack stimulates accumulation of abscisic acid (ABA) that activates a number of genes associated with wound suberization of plants. Cytochrome P450 fatty acid ω-hydroxylase CYP86A1 catalyzes ω-hydroxylation of fatty acids to form the ω-functionalized monomers that play a pivotal role in suberin synthesis. However, the transcriptional regulation of ABA signaling on AchnCYP86A1 has not been characterized in kiwifruit. In this study, AchnCYP86A1, a kiwifruit homolog of Arabidopsis AtCYP86A1, was isolated. AchnCYP86A1-overexpressed N. benthamiana leaves displayed that the AchnCYP86A1 functioned as a fatty acid ω-hydroxylase associated with synthesis of suberin monomer. The regulatory function of three transcription factors (TFs, including AchnMYC2, AchnMYB41 and AchnMYB107) on AchnCYP86A1 was identified. All the three TFs were localized in nucleus and could individually interact with AchnCYP86A1 promoter to activate gene expression in yeast one-hybrid and dual-luciferase assays. The findings were further demonstrated in transient overexpressed N. benthamiana, in which all TFs notably elevated the expression of aliphatic synthesis genes including CYP86A1 and the accumulation of ω-hydroxyacids, α, ω-diacids, fatty acids and primary alcohols. Moreover, exogenous ABA induced the expression of AchnMYC2, AchnMYB41 and AchnMYB107 that promoted AchnCYP86A1 involving in suberin monomer formation. Contrary to the inductive effects of ABA, however, fluridone (an inhibitor of ABA biosynthesis) inhibited the three TFs expression and suberin monomer formation. These results indicate that AchnMYC2, AchnMYB41 and AchnMYB107 positively regulate suberin monomer synthesis by activating AchnCYP86A1 promoter in response to ABA.

Highlights

Plants have specialized cutin and suberin that deposit in the cell walls to protect them from environmental stress, such as drought and wound pathogen attack (Pollard et al, 2008)
Phylogenetic tree showed that AchnCYP86A1 was closely grouped together with StCYP86A33, AtCYP86A1 and NbCYP86A1 (Figure S1A), suggesting that AchnCYP86A1 was homologous to AtCYP86A1 and StCYP86A33 that could catalyze the w-hydroxylation of fatty acids to w-hydroxyacids in suberin synthesis (Höfer et al, 2008; Serra et al, 2009)
Genes involved in aliphatics synthesis have been identified in potato, Arabidopsis and cork (Soler et al, 2007; Vishwanath et al, 2015)

Summary

Introduction

Plants have specialized cutin and suberin that deposit in the cell walls to protect them from environmental stress, such as drought and wound pathogen attack (Pollard et al, 2008). Mutants of AtCYP86A1 and silencing of StCYP86A33, a potato homolog of AtCYP86A1, have been demonstrated that the CYP86A1 is mainly responsible for production of whydroxyacids in suberin synthesis (Höfer et al, 2008; Serra et al, 2009). Based on these investigations, the CYP86A1 seems to be a strong candidate for the enzyme implicated in the w-hydroxylation of fatty acids in suberin synthesis

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Conclusion