Natural Variation in CRABS CLAW contributes to fruit length divergence in cucumber

Authors: CHE, GAN - China Agricultural University; PAN, YUPENG - University Of Wisconsin; LIU, XIAOFENG - China Agricultural University; LI, MIN - China Agricultural University; ZHAO, JIANYU - University Of Wisconsin; YAN, SHUANGSHUAN - China Agricultural University; YUTING, HE - China Agricultural University; WANG, ZHONGYI - China Agricultural University; CHENG, ZHIHUA - China Agricultural University; SONG, WEIYUAN - China Agricultural University; ZHOU, ZHONGYANG - China Agricultural University; WU, TAO - China Agricultural University; Weng, Yiqun; ZHANG, XIAOLAN - China Agricultural University

Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2022
Publication Date: 11/25/2022
Citation: Che, G., Pan, Y., Liu, X., Li, M., Zhao, J., Yan, S., Yuting, H., Wang, Z., Cheng, Z., Song, W., Zhou, Z., Wu, T., Weng, Y., Zhang, X. 2022. Natural Variation in CRABS CLAW contributes to fruit length divergence in cucumber. The Plant Cell. 35(2). https://doi.org/10.1093/plcell/koac335.
DOI: https://doi.org/10.1093/plcell/koac335

Interpretive Summary: Fruit length is a key domestication trait that affects crop yield and appearance quality. Cucumber fruits vary from 5~60 cm in length. Despite multiple fruit length QTLs having been identified, the underlying genes and regulatory mechanisms are poorly understood. We conducted map-based cloning of the fruit size QTL, FS5.2 that controls fruit elongation and radial growth involving the semi-wild XIS cucumber. We identified a single nucleotide polymorphism (SNP, G to A) in the cucumber gene, CRABS CLAW (CsCRC) which is the candidate gene of FS5.2. The A allele only exists in the XIS cucumber bearing round fruit. When the A allele was introduced to long fruit background, it can cause 34~39% reduction in fruit length. Transgenic cucumber with reduced expression of the G allele showed reduced fruit length and decreased cell size. We identified an auxin responsive protein CsARP1 that is the downstream target gene of CsCRC. This work suggests that CsCRC positively regulates fruit elongation through transcriptional activation of CsARP1 and thus enhanced cell expansion. This work provides insights into molecular mechanisms of fruit size control in cucumber by the CRC gene. Utilization of CsCRC alleles may also provide a strategy to manipulate fruit length in cucumber breeding.

Technical Abstract: Fruit length is a key domestication trait that affects crop yield and appearance quality. Cucumber fruits vary from 5~60 cm in length. Despite multiple fruit length QTLs having been identified, the underlying genes and regulatory mechanisms are poorly understood. Map-based cloning identified a nonsynonymous SNP (G to A) in CRABS CLAW (CsCRC) confers the major effect fruit length QTL FS5.2. CsCRCA is a rare allele only exist in Xishuangbanna cucumber with round fruits. Construction of near-isogenic line (NIL) of CsCRCA led to 34~39% reduction in fruit length. Introduction of CsCRCG into the NIL rescued the short-fruit phenotype, and knockdown of CsCRCG resulted in reduced fruit length and decreased cell size. Further, an auxin responsive protein CsARP1 is the downstream target gene of CsCRCG, instead of CsCRCA. Knockout of CsARP1 produced decreased fruit length with smaller cells. Hence, our work suggested that CsCRCG positively regulates fruit elongation through transcriptional activation of CsARP1 and thus enhanced cell expansion. Utilization of CsCRC alleles provides a new strategy to manipulate fruit length in cucumber breeding.