14-3-3 Proteins Are Involved in BR-Induced Ray Petal Elongation in Gerbera hybrida.

Xiaohui Lin,Yanbo Chen,Xiaojing Wang,Yaqin Wang,Shina Huang,Gan Huang

doi:10.3389/fpls.2021.718091

Abstract

14-3-3 proteins play a major role in the regulation of primary metabolism, protein transport, ion channel activity, signal transduction and biotic/abiotic stress responses. However, their involvement in petal growth and development is largely unknown. Here, we identified and characterized the expression patterns of seven genes of the 14-3-3 family in gerbera. While none of the genes showed any tissue or developmental specificity of spatiotemporal expression, all seven predicted proteins have the nine α-helices typical of 14-3-3 proteins. Following treatment with brassinolide, an endogenous brassinosteroid, the Gh14-3-3 genes displayed various response patterns; for example, Gh14-3-3b and Gh14-3-3f reached their highest expression level at early (2 h) and late (24 h) timepoints, respectively. Further study revealed that overexpression of Gh14-3-3b or Gh14-3-3f promoted cell elongation, leading to an increase in ray petal length. By contrast, silencing of Gh14-3-3b or Gh14-3-3f inhibited petal elongation, which was eliminated partly by brassinolide. Correspondingly, the expression of petal elongation-related and brassinosteroid signaling-related genes was modified in transgenic petals. Taken together, our research suggests that Gh14-3-3b and Gh14-3-3f are positive regulators of brassinosteroid-induced ray petal elongation and thus provides novel insights into the molecular mechanism of petal growth and development.

Highlights

14-3-3 proteins, with a molecular weight of 25∼32 kDa, are a class of highly conserved, acidic, soluble proteins that are present in almost all eukaryotes (Ferl, 1996; Mhawech, 2005)
Gh143-3c is located in the ε branch of the tree, while the other six Gh14-3-3 proteins belong to the non-ε group
The results suggest that Gh14-3-3b and Gh14-3-3f promote ray petal elongation by regulating cell elongation

Summary

Introduction

14-3-3 proteins, with a molecular weight of 25∼32 kDa, are a class of highly conserved, acidic, soluble proteins that are present in almost all eukaryotes (Ferl, 1996; Mhawech, 2005). Each 14-3-3 isoform contains nine α-helices and shows a high degree of similarity to other 14-3-3 members (Aitken, 2006) As bridge proteins, they participate widely in the regulation of various physiological processes (including metabolism, hormone signaling and stress response) by interacting with numerous clients, such as metabolic enzymes, signaling proteins and transcription factors (Silva et al, 2001; Chevalier et al, 2009; Zhou et al, 2015; Li M. et al, 2016; Keicher et al, 2017; Camoni et al, 2018). Zuo et al (2021) identified eighteen 14-3-3 genes in the apple genome and characterized their expression patterns, suggesting that some of them may participate in the regulation of the flowering process These results all highlight the importance of 14-3-3 proteins in plant growth. Whether 14-3-3 proteins, as one of the BR signaling components, play a regulatory role in BR-induced petal elongation in gerbera, or in any other flowering species, remains unknown

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