ClZISO mutation leads to photosensitive flesh in watermelon

• Published in: Theoretical and applied genetics Vol. 135; no. 5; pp. 1565 - 1578
• Main Authors: Zhang, Jie, Sun, Honghe, Guo, Shaogui, Ren, Yi, Li, Maoying, Wang, Jinfang, Yu, Yongtao, Zhang, Haiying, Gong, Guoyi, He, Hongju, Zhang, Chao, Xu, Yong
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2022; Springer; Springer Nature B.V
• Subjects: Abscisic acid; Agricultural research; Agriculture; Biochemistry; Biomedical and Life Sciences; Biosynthesis; Biotechnology; Carotenoids; Chromatophores; Citrullus lanatus; Color; Color of plants; Gene mutations; Genetic aspects; Life Sciences; Mutants; Mutation; Nonsense mutation; Original Article; Physiological aspects; Plant Biochemistry; Plant Breeding/Biotechnology; Plant Genetics and Genomics; Stop codon; Transcriptomes; Transversion; Watermelons; China
• ISSN: 0040-5752; 1432-2242
• DOI: 10.1007/s00122-022-04054-7

Key message The mutation of ClZISO identified in EMS-induced watermelon leads to photosensitive flesh in watermelon. Watermelon ( Citrullus lanatus ) has a colorful flesh that attracts consumers and benefits human health. We developed an ethyl-methanesulfonate mutation library in red-fleshed line ‘302’ to create new flesh color lines and found a yellow-fleshed mutant which accumulated ζ-carotene. The initial yellow color of this mutant can be photobleached within 10 min under intense sunlight. A long-term light-emitting diode (LED) light treatment turned flesh color from yellow to pink. We identified this unique variation as photosensitive flesh mutant (‘ psf ’). Using bulked segregant analysis, we fine-mapped an EMS-induced G-A transversion in ‘ psf ’ which leads to a premature stop codon in 15- cis -ζ-carotene isomerase ( ClZISO ) gene. We detected that wild-type ClZISO is expressed in chromoplasts to catalyze the conversion of 9,15,9’-tri- cis -ζ - carotene to 9,9’-di- cis -ζ-carotene. The truncated ClZISO mu protein in psf lost this catalytic function. Light treatment can partially compensate ClZISO mu isomerase activity via photoisomerization in vitro and in vivo. Transcriptome analysis showed that most carotenoid biosynthesis genes in psf were downregulated. The dramatic increase of ABA content in flesh with fruit development was blocked in psf . This study explores the molecular mechanism of carotenoid biosynthesis in watermelon and provides a theoretical and technical basis for breeding different flesh color lines in watermelon.