A Functional Allele of Regulates Fruit Length through Repressing and Inhibiting Auxin Transport in Cucumber.

Fruit length is a prominent agricultural trait during cucumber () domestication and diversifying selection; however, the regulatory mechanisms of fruit elongation remain elusive. We identified two alleles of the ()-like MADS-box gene with 3393 Single Nucleotide Polymorphism variation among 150 cucumber lines. Whereas was specifically enriched in the long-fruited East Asian type cucumbers (China and Japan), the allele was randomly distributed in cucumber populations, including wild and semiwild cucumbers. knockdown led to further fruit elongation in cucumber, whereas elevated expression of resulted in significantly shorter fruits. No effect on fruit elongation was detected when expression was modulated, suggesting that is a gain-of-function allele in long-fruited cucumber that acts as a repressor during diversifying selection of East Asian cucumbers. Furthermore, binds to the CArG-box in the promoter region of , a regulator of cell division and expansion, to repress its expression. Additionally, inhibits the expression of auxin transporters () and , resulting in decreases in auxin accumulation in fruits. Together, our work identifies an agriculturally important allele and suggests a strategy for manipulating fruit length in cucumber breeding that involves modulation of expression.