Novel Bisexual Flower Control Gene Regulates Sex Differentiation in Melon (Cucumis melo L.)

Abstract

The sex-control system involves several mechanisms in melon. The present study identified a novel bisexual flower control gene from the hermaphroditic melon germplasm, different from the previously recognized one. Genetic analysis showed that a single recessive gene in the newly identified locus b controlled the bisexual flower phenotype in melons. We generated 1431 F 2 segregating individuals for genetic mapping of locus b, which was delimited to a 47.94 kb region. Six candidate genes were identified in the delimited interval, and candidate No. 4 encoding melon CPR5 protein was selected as the suitable one for locus b and was denoted CmCPR5. CPR5 reportedly interacted with ethylene receptor ETR1 to regulate ethylene signal transduction. Moreover, the ethephon assays showed that the parental lines (unisexual line and bisexual line) had contrasting expression patterns of CmCPR5. The BiFC and LCI assays also confirmed that CmCPR5 interacted with CmETR1 in 0426 but not in Y101. However, crossover tests showed that CmETR1 functioned normally in both parental lines, suggesting CPR5 malfunction in Y101. This study proposed a corollary mechanism of bisexual flower regulation during stamen primordium development in which the inhibition of stamen primordia development was prevented by the malfunctioning CmCPR5, resulting in bisexual flowers.

Identification of novel sex determination loci in Japanese weedy melon

“… CmCPR5 sequence variation among ‘DHL92’ (reference genome), EF and UT1 (sequenced in this study), and the hermaphrodite line Y101 and monoecious line 0426 (Wang et al 2022). Gray shading indicates SNPs in the coding sequence.…”

“…A novel bisexual flower control gene has been identified on Chr. 8 of a hermaphroditic melon germplasm (Wang et al 2022), and a novel sex determination gene, CmCRC , has been identified on Chr. 10 (Zhang et al, 2022).…”

Identification of key genes promoting stamen formation induced by silver nitrate in gynoecious melon

“…In this study, transcriptome sequencing was used to analyze the DEGs between the flower buds of the gynoecious melon WI998 treated with 450 mg/L AgNO 3 and untreated flower buds. Previous studies have found the key period for stamen development is when flower buds reach a size of 0.3–2 mm (Q. Wang et al., 2009). We, therefore, used flower buds with diameters of 2 mm in this study.…”

Advance in sex differentiation in cucumber

“…Early in cucumber bud development, both the androgynophores appear ( Atsmon, 1960 ; Moraes, 2020 ); however, with the gradual growth and development of the plant, only one pistil primordium or stamen primordium can continue to develop, and the other gradually degenerates through apoptosis, thus forming a female or male flower ( Perl-Treves, 2004 ). If the growth of both male and female flowers is not restricted, they will develop into bisexual flowers ( Malepszy and Niemirowicz-Szczytt, 1991 ; Wang et al., 2022 ).…”

“…In 2009, the M gene was cloned, and a SNP site (G97T) linked to the M gene was found in the first exon of the CsACS2 gene, resulting in a heterozygous mutation of amino acid G33C ( Li et al., 2009 ; Wang et al., 2022 ); in the same year, in other experiments, three types of heterozygous mutations of CsACS2 were obtained in cucumber germplasm: G33C, P209S, and S399L, and the results of enzyme activity assay showed that the enzyme activity of CsACS2 was reduced or even completely inactivated after the three types of mutations ( Boualem et al., 2009 ). Finally, we concluded that CsACS2 is an M gene that encodes an ACC synthase.…”