The GhmiR157a-GhSPL10 regulatory module controls initial cellular dedifferentiation and callus proliferation in cotton by modulating ethylene-mediated flavonoid biosynthesis.

Lichen Wang,Tianyi Wang,Keith Lindsey,Xianlong Zhang,Jianying Li,Tianwang Wen,Nian Liu,Xiyan Yang

doi:10.1093/jxb/erx475

Lichen Wang, Tianyi Wang + Show 6 more

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https://doi.org/10.1093/jxb/erx475

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Abstract

MicroRNAs (miRNAs) modulate many biological processes through inactivation of specific mRNA targets such as those encoding transcription factors. A delicate spatial/temporal balance between specific miRNAs and their targets is central to achieving the appropriate biological outcomes. Somatic embryogenesis in cotton (Gossypium hirsutum), which goes through initial cellular dedifferentiation, callus proliferation, and somatic embryo development, is of great importance for both fundamental research and biotechnological applications. In this study, we characterize the function of the GhmiR157a-GhSPL10 miRNA-transcription factor module during somatic embryogenesis in cotton. We show that overexpression of GhSPL10, a target of GhmiR157a, increases free auxin and ethylene content and expression of associated signaling pathways, activates the flavonoid biosynthesis pathway, and promotes initial cellular dedifferentiation and callus proliferation. Inhibition of expression of the flavonoid synthesis gene F3H in GhSPL10 overexpression lines (35S:rSPL10-7) blocked callus initiation, while exogenous application of several types of flavonol promoted callus proliferation, associated with cell cycle-related gene expression. Inhibition of ethylene synthesis by aminoethoxyvinylglycine treatment in the 35S:rSPL10-7 line severely inhibited callus initiation, while activation of ethylene signaling through 1-aminocyclopropane 1-carboxylic acid treatment, EIN2 overexpression, or inhibition of the ethylene negative regulator CTR1 by RNA interference promoted flavonoid-related gene expression and flavonol accumulation. These results show that an up-regulation of ethylene signaling and the activation of flavonoid biosynthesis in GhSPL10 overexpression lines were associated with initial cellular dedifferentiation and callus proliferation. Our results demonstrate the importance of a GhmiR157a-GhSPL10 gene module in regulating somatic embryogenesis via hormonal and flavonoid pathways.

Highlights

Plant cells exhibit developmental plasticity manifested by diverse tissue or organ regeneration pathways, which can be classified into two main types, de novo organogenesis and somatic embryogenesis (SE) (Ikeuchi et al, 2016).Ethylene plays an important hormonal role during plant growth and development
AtSPL10 and AtSPL11 are involved in zygotic embryogenesis in Arabidopsis (Nodine and Bartel, 2010), and we identified four other cotton homologues (Gh_A12G0866, Gh_D12G0947, Gh_A11G0706, and Gh_D11G0821) that exhibit strong similarity to AtSPL10/11; all harbor GhmiR157a target sites (Supplementary Fig. S1)
The concentration of endogenous indole-3-acetic acid (IAA) was measured in the different lines by HPLC-Murashige and Skoog (MS), and the results showed that free IAA concentration increased in the hypocotyls of 35S:resistant GhSPL10 (rSPL10)-7, while the most prevalent IAA conjugate, IAA–Asp, decreased, implying that the IAA signaling pathway might be altered in GhSPL10 overexpression lines

Summary

Introduction

Plant cells exhibit developmental plasticity manifested by diverse tissue or organ regeneration pathways, which can be classified into two main types, de novo organogenesis and somatic embryogenesis (SE) (Ikeuchi et al, 2016).Ethylene plays an important hormonal role during plant growth and development. Plant cells exhibit developmental plasticity manifested by diverse tissue or organ regeneration pathways, which can be classified into two main types, de novo organogenesis and somatic embryogenesis (SE) (Ikeuchi et al, 2016). The ethylene signaling pathway is initiated from a receptor complex that includes ETHYLENE RESISTANT1 (ETR1), which in the presence of ethylene. Several pieces of evidence implicate ethylene as an endogenous stimulator of cell division. Ethylene promotes cambium cell division in Populus during tension wood production (Love et al, 2009)

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