The transcription factor CpMYB62 controls the genetic network that leads to the determination of female flowers in Cucurbita pepo

Abstract

In monoecious species, female flowering constitutes the developmental process that determines the onset and production of fruit and is therefore closely related to crop yield. This article presents the identification and phenotypic and molecular characterization of myb62, an ethylmethane sulfonate loss-of-function mutation that completely blocks the female floral transition, converting all female flowers into male flowers. BSA-seq analysis coupled with WGS showed that myb62 corresponds to a C>T transition in the coding region of the gene CpMYB62, generating a premature stop codon and a truncated transcription factor without its N-terminal effector domain. The myb62 phenotype was partially rescued by exogenous ethylene application, indicating that the function of CpMYB62 is mediated by ethylene. Different evidence supports this conclusion: first, the reduced ethylene production of the mutant, and second, the male flower productive phenotype of the double mutant between myb62 and the ethylene-insensitive mutant etr2b, which demonstrated that myb62 is epistatic over etr2b. Furthermore, transcriptomic analysis of WT and myb62 apical shoots confirmed that CpMYB62 regulates master sex-determining genes, upregulating those encoding the ethylene biosynthesis enzymes CpACO2B and CpACS27A and those encoding for transcription factors that promote the development of carpels (CpCRC), but downregulating those involved in the arrest of carpels (CpWIP1). In the gene network controlling sex determination in cucurbits, CpMYB62 occupies the most upstream position, activating ethylene and other sex determining genes involved in female flower determination in Cucurbita pepo.

Acknowledgements

This work was supported by grant PID2020-118080RB-C21, funded by the Spanish Ministry of Science and Innovation together with EU FEDER funds. M.S. acknowledges the D.I scholarship program from MCI with the company Green Breeding Biotech SL, J.I.-M. acknowledges the FPI scholarship program from MEC, and A.G. received a Margarita Salas postdoctoral fellowship.

Author contributions

M.J. and C.M.: design and coordination of the research; M.S.: conducting most of the experiments and data analysis; A.G., A.B., J.I.-M., and G.G.: collaboration in data analysis; M.J., C.M., and M.S.: writing and revision. All authors contributed to the article and approved the submitted version.

Data availability

All relevant data can be found within the manuscript and its supporting materials. All the raw reads generated in this study have been deposited in the public database of the National Center of Biotechnology under BioProject Number PRJNA1018819 and PRJNA1042934.

Conflict of interest statement

The authors declare no conflict of interest regarding this publication.

Supplementary Data

Supplementary data is available at Horticulture Research online.

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