Gynoecy instability in cucumber (Cucumis sativus L.) is due to unequal crossover at the copy number variation-dependent Femaleness (F) locus

Abstract

Cucumber, Cucumis sativus is an important vegetable crop, and gynoecy has played a critical role in yield increase of hybrid cucumber production. Cucumber has a unique genetic system for gynoecious sex expression, which is determined by the copy number variation (CNV)-based, dominant, and dosage-dependent femaleness (F) locus. However, this gynoecy expression system seems unstable since monecious plants could often be found in Fdependent gynoecious cucumber inbreds. We hypothesized that gynoecy instability (gynoecy loss) may be due to unequal crossing over (UCO) during meiosis among repeat units of the CNV. In this study, using high throughput genome resequencing, fiber-FISH and genomic qPCR analyses, we first confirmed and refined the structure of the F locus, which was a CNV of a 30.2-kb tandem repeat. Gynoecious plants contained three genes: CsACS1, CsACS1G, and CsMYB, of which CsACS1G is a duplication of CsACS1 but with a recombinant distal promoter that may contribute to gynoecy sex expression. In two large populations from self-pollinated gynoecious inbred lines, 'gynoecy loss' mutants were identified with similar mutation rates (~0.12%). We show that these monecious mutants have lost CsACS1G. In addition, we identified gynoecious lines in natural populations that carry two copies of CSACS1G. We proposed a model to explain gynoecy instability in F-dependent cucumbers, which is caused by UCO among CSACS1/G units during meiosis. The findings present a convincing case that the phenotypic variation of an economically important trait is associated with the dynamic changes of copy numbers at the F locus. This work also has important implications in cucumber breeding.

Improving Agrobacterium tumefaciens−Mediated Genetic Transformation for Gene Function Studies and Mutagenesis in Cucumber (Cucumis sativus L.)

“…Seeds of 9930 and WI7602 were kindly supplied by Xingfang Gu (Chinese Academy of Agricultural Sciences, Beijing, China) and Sen Li (Shanxi Agricultural University, China), respectively. Gy14M (also known as Gy14M42) is the monoecious version of the gynoecious Gy14 [ 41 ]. H19 is a littleleaf ( LL ) mutant [ 25 ].…”

Fine-mapping and candidate gene analysis of the Mcgy1 locus responsible for gynoecy in bitter gourd (Momordica spp.)

“…ACS encodes a 1-aminocyclopropane-1-carboxylic acid (ACC) synthase catalysing the conversion of S-adenosylmethionine (SAM) to form ACC, and ethylene is then synthesized from ACC, which is catalysed by ACC oxidase encoded by ACO (Boualem et al, 2015). For example, a unique F locus associated with gynoecy was identi ed in cucumber, and previous works have suggested that monoecious plants carry only one CsACS1 gene, while gynoecious plants have not only the CsACS1 gene but also an additional copy of CsACS1 named CsACS1G (F) (Mibus & Tatlioglu, 2004;Li et al, 2020). The loss of function of the androecy (a) gene CsACS11/CmACS11, which is the hypostatic gene of F and controls female ower development, leads to androecious cucumber and melon plants (Boualem et al, 2015).…”

Identification of a major QTL, Parth6.1 associated with parthenocarpic fruit development in slicing cucumber genotype, Pusa Parthenocarpic Cucumber-6

“…QTL-seq combines the next-generation sequencing technology with BSA for rapid detection of QTLs for any particular trait and facilitate development of closely associated molecular markers and identification of candidate genes. Thereafter, QTL-seq has been widely used for the detection of QTLs, identification of closely linked molecular markers and identification of candidate genes for number of traits in different crops ( Singh et al., 2016 ; Wang et al., 2016 ; Wei et al., 2016 ; Chen et al., 2017 ; Wen et al., 2019 ; Arikit et al., 2019 ; Li et al., 2020 ). In cucumber, QTL-seq has been used successfully for the identification of QTL for early flowering traits ( Lu et al., 2014 ), flesh thickness ( Xu et al., 2015 ), sub-gynoecy sex expression ( Win et al., 2019 ), pre-harvest sprouting of the seeds ( Cao et al., 2021 ) and resistance to powdery mildew ( Zhang et al., 2021 ).…”