Genetic Regulation of Ethylene Dosage for Cucumber Fruit Elongation

Abstract

Plant organ growth and development are determined by a subtle balance between growth stimulation and inhibition. Fruit size and shape are important quality traits influencing yield and market value; however, the underlying mechanism regulating the balance of fruit growth to achieve final size and shape is not well understood. Here, we report a mechanistic model that governs cucumber (Cucumis sativus) fruit elongation through fine-tuning of ethylene homeostasis. We identified a cucumber mutant that bears short fruits owing to repressed cell division. SF1 (Short Fruit 1) encodes a cucurbit-specific RING-type E3 ligase, and the mutation resulted in its enhanced self-ubiquitination and degradation, but accumulation of ACS2 (1-aminocyclopropane-1-carboxylate synthase 2), a rate-limiting enzyme for ethylene biosynthesis. The overproduction of ethylene contributes to the short-fruit phenotype of sf1. Dysfunction of ACS2 resulted in reduced ethylene production, but still repressed cell division and shorter fruit, suggesting that ethylene is still required for basal fruit elongation. SF1 ubiquitinates and degrades both itself and ACS2 to control ethylene synthesis for dose-dependent effect on cell division and fruit elongation. Our findings reveal the mechanism by which ethylene dosage is regulated for the control of cell division in developing fruit.

Localization of quantitative trait loci for cucumber fruit shape by a population of chromosome segment substitution lines

“…In addition, SF1 was localized in the region of 5.10-14.23 Mb on chromosome 2 in which FS2.1 was mapped in our study and previous studies ( Supplementary Fig. S4) 17,19 . However, there is no difference in protein sequence and gene expression of SF1 between RNS7 and CNS21.…”

Resequencing of 297 melon accessions reveals the genomic history of improvement and loci related to fruit traits in melon

“…In 2015 and 2016 field trials, the mean FSI of 117 3‐carpel accessions was 1.43 ± 0.42 and 1.46 ± 0.50, while those for the 32 5‐carpel were 1.07 ± 0.18 and 1.06 ± 0.18, respectively, indicating 5‐carpel fruits tend to be rounder than 3‐carpel fruits. In melon and cucumber, plants with andromonoecious or hermaphroditic sex expression often produce round fruits (Boualem et al ., 2008; Pan et al ., 2020b; Tan et al ., 2015; Xin et al ., 2019). This interesting relationship may be due to the pleiotropic effects of the andromonoecy ( a / CmACS7 ) gene in melon and the m / CsACS2 gene in cucumber, which is probably related to the ethylene accumulation level, rather than the tight linkage to FS genes (Boualem et al ., 2008; Galpaz et al ., 2018).…”

The curvature of cucumber fruits is associated with spatial variation in auxin accumulation and expression of a YUCCA biosynthesis gene

“…The fruit shape obtained at the end of this process depends on the ovary shape and is controlled by preanthesis processes 5 . In addition, several hormones regulate fruit elongation and shape in response to environmental stimuli 6 . For instance, the endogenous level of auxin is closely associated with fruit shape, set, and size 7 .…”