J Integr Plant Biol. ›› 2021, Vol. 63 ›› Issue (7): 1341-1352.DOI: 10.1111/jipb.13088

• Molecular Physiology • Previous Articles     Next Articles

Alternative splicing of MaMYB16L regulates starch degradation in banana fruit during ripening

Guoxiang Jiang1†, Dandan Zhang1†, Zhiwei Li1,3, Hanzhi Liang1,3, Rufang Deng1, Xinguo Su4, Yueming Jiang1,2 and Xuewu Duan1,2*   

  1. 1 South China Botanical Garden, the Chinese Academy of Sciences, Guangzhou 510650, China
    2 Center of Economic Botany, Core Botanical Gardens, the Chinese Academy of Sciences, Guangzhou 510650, China
    3 College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China 4. Guangdong AIB Polytechnic, Guangzhou 510507, China

    These authors contributed equally to this work.
    *Correspondence: Xuewu Duan (xwduan@scbg.ac.cn)
  • Received:2020-12-27 Accepted:2021-03-02 Online:2021-03-03 Published:2021-07-01

Abstract: The alternative splicing of select genes is an important mechanism to regulate responses to endogenous and environmental signals in plants. However, the role of alternative splicing in regulating fruit ripening remains unclear. Here, we discovered that MaMYB16L, an R1-type MYB transcription factor, undergoes alternative splicing and generates two transcripts, the full-length isoform MaMYB16L and a truncated form MaMYB16S, in banana fruit. During banana fruit ripening, the alternative splicing process intensifies with downregulated MaMYB16L and upregulated MaMYB16S. Moreover, MaMYB16L is a transcriptional repressor that directly binds with the promoters of many genes associated with starch degradation and MaDREB2, a positive ripening regulator, and represses their expression. In contrast, MaMBY16S lacks a DNA-binding domain but competitively combines and forms non-functional heterodimers with functional MaMYB16L. MaMYB16L-MaMYB16S heterodimers decrease the binding capacity and transrepression activity of MaMYB16L. The downregulation of MaMYB16L and the upregulation of MaMYB16S, that is, a decreased ratio of active to non-active isoforms, facilitates the activation of ripening-related genes and thereby promotes fruit ripening. Furthermore, the transient overexpression of MaMYB16S promotes banana fruit ripening, whereas the overexpression of MaMYB16L delays this process. Therefore, the alternative splicing of MaMYB16L might generate a self-controlled regulatory loop to regulate banana fruit ripening.

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