A Functional Allele of CsFUL1 Regulates Fruit Length through Repressing CsSUP and Inhibiting Auxin Transport in Cucumber

Abstract

Fruit length is a prominent agricultural trait during cucumber (Cucumis sativus) domestication and diversifying selection; however, the regulatory mechanisms of fruit elongation remain elusive. We identified two alleles of the FRUITFULL (FUL)-like MADS-box gene CsFUL1 with 3393 C/A Single Nucleotide Polymorphism variation among 150 cucumber lines. Whereas CsFUL1 A was specifically enriched in the long-fruited East Asian type cucumbers (China and Japan), the CsFUL1 C allele was randomly distributed in cucumber populations, including wild and semiwild cucumbers. CsFUL1 A knockdown led to further fruit elongation in cucumber, whereas elevated expression of CsFUL1 A resulted in significantly shorter fruits. No effect on fruit elongation was detected when CsFUL1 C expression was modulated, suggesting that CsFUL1 A is a gain-of-function allele in long-fruited cucumber that acts as a repressor during diversifying selection of East Asian cucumbers. Furthermore, CsFUL1 A binds to the CArG-box in the promoter region of SUPERMAN, a regulator of cell division and expansion, to repress its expression. Additionally, CsFUL1 A inhibits the expression of auxin transporters PIN-FORMED1 (PIN1) and PIN7, 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 CsFUL1 A expression.

A fast, simple, high efficient and one-step generation of composite cucumber plants with transgenic roots by Agrobacterium rhizogenes-mediated transformation

“…Cucumber (Cucumis sativus L.) is an economically and nutritionally important, and one of the top 5 vegetable crops cultivated worldwide (Liu et al 2011;Zhao et al 2019). In 2017, more than 83.8 million tons cucumbers (including gherkins) are globally produced.…”

Genome-wide analysis of OVATE family proteins in cucumber (Cucumis sativus L.)

“…Recent studies revealed that several OFPs negatively control the fruit length. For example, both OVATE and SlOFP20 regulate fruit length in tomato [1,21]. In melon (Cucumis melo), six candidate genes in a QTL associated with shape on chromosome 8 include CmOFP13.…”

“…Moreover, a MADS-box transcription factor CsFUL1 negatively regulate fruit length via inhibits the expression of SUPERMAN and auxin transporters PIN1/7 [20]. Although these OFPs have been studied several plant species, only CsOFP15a was reported as a candidate gene regulating the fruit length in cucumber [21]. But whether CsOFP members regulate cucumber fruit development remains largely unknown.…”

A Growing Reputation for FRUITFULL Genes

“…Fruit length is an important parameter in cucumber (Cucumis sativus) breeding; however, few candidate genes underlying this trait have been identified, while none have been validated. Now, Zhao et al (2019) have revealed how the activities of the MADS domain transcription factor FRUITFULL (FUL) have been modulated in cucumber to regulate fruit length.…”

“…Together, these results suggest that the mutation in the K domain Fruits from a selection of cucumber plant lines used for a genome-wide association study for fruit length. (Adapted from Zhao et al, 2019, Figure 2A) [OPEN] Articles can be viewed without a subscription. www.plantcell.org/cgi/doi/10.1105/tpc.19.00194 of CsFUL1 A modulates protein-protein interactions, which rewires the gene regulatory network underlying fruit growth.…”