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Article|30 Jan 2023|OPEN
CsTRM5 regulates fruit shape via mediating cell division direction and cell expansion in cucumber
Yang Xie1 ,† , Xiaofeng Liu2,3 ,† , Chengzhen Sun1 ,† , Xiaofei Song1 , Xiaoli Li1 , Haonan Cui1 , Jingyu Guo2 , Liu Liu2 , Ao Ying2 , Zeqin Zhang2 , Xueyun Zhu1 and Liying Yan1 , , Xiaolan Zhang,2 ,
1Hebei Key Laboratory of Horticultural Germplasm Excavation and Innovative Utilization, College of Horticulture Science and Technology, Hebei Normal University of Science and Technology, Qinhuangdao 066004, China
2State Key Laboratories of Agrobiotechnology, Joint International Research Laboratory of Crop Molecular Breeding, Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Sciences, China Agricultural University, Beijing 100193, China
3Engineering Laboratory of Genetic Improvement of Horticultural Crops of Shandong Province, College of Horticulture, Qingdao Agricultural University, Qingdao 266109, China
*Corresponding author. E-mail: yanliying0665@hevttc.edu.cn,zhxiaolan@cau.edu.cn
Yang Xie,Xiaofeng Liu,Chengzhen Sun contributed equally to the study.

Horticulture Research 10,
Article number: uhad007 (2023)
doi: https://doi.org/10.1093/hr/uhad007
Views: 254

Received: 27 Jan 2022
Accepted: 18 Jan 2023
Published online: 30 Jan 2023

Abstract

Fruit shape and size are important appearance and yield traits in cucumber, but the underlying genes and their regulatory mechanisms remain poorly understood. Here we identified a mutant with spherical fruits from an Ethyl Methane Sulfonate (EMS)-mutagenized library, named the qiu mutant. Compared with the cylindrical fruit shape in 32X (wild type), the fruit shape in qiu was round due to reduced fruit length and increased fruit diameter. MutMap analysis narrowed the candidate gene in the 6.47 MB range on Chr2, harboring the FS2.1 locus reported previously. A single-nucleotide polymorphism (SNP) (11359603) causing a truncated protein of CsaV3_2G013800, the homolog of tomato fruit shape gene SlTRM5, may underlie the fruit shape variation in the qiu mutant. Knockout of CsTRM5 by the CRISPR-Cas9 system confirmed that CsaV3_2G013800/CsTRM5 was the causal gene responsible for qiu. Sectioning analysis showed that the spherical fruit in qiu resulted mainly from increased and reduced cell division along the transverse and longitudinal directions, respectively. Meanwhile, the repressed cell expansion contributed to the decreased fruit length in qiu. Transcriptome profiling showed that the expression levels of cell-wall-related genes and abscisic acid (ABA) pathway genes were significantly upregulated in qiu. Hormone measurements indicated that ABA content was greatly increased in the qiu mutant. Exogenous ABA application reduced fruit elongation by inhibiting cell expansion in cucumber. Taken together, these data suggest that CsTRM5 regulates fruit shape by affecting cell division direction and cell expansion, and that ABA participates in the CsTRM5-mediated cell expansion during fruit elongation in cucumber.