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

Update Time: 2017-12-28 10:46:27Click:96 times
Lichen Wang, Nian Liu, Tianyi Wang, Jianying Li, Tianwang Wen, Xiyan Yang*, Keith Lindsey, Xianlong Zhang.2017.Journal of Experimental Botany

Abstract

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