Tandem 13-Lipoxygenase Genes in a Cluster Confers Yellow-Green Leaf in Cucumber

Abstract

Some lipoxygenase (LOX) isoenzymes can co-oxidize carotenoids. Carotenoids are collectors of light energy for photosynthesis and can protect plants from reactive oxygen species and coloration. This study isolated the cucumber (Cucumis sativus L.) yellow-green leaf mutant (ygl1), which had yellow-green leaves with decreased chlorophyll synthesis, increased relative carotenoid content, and delayed chloroplast development. Genetic analysis demonstrated that the phenotype of ygl1 was caused by a recessive mutation in a nuclear gene. The bulked segregants were resequenced, and the candidate ygl1 locus identified was mapped to the 9.2 kb region of the chromosome 4. Sequence analysis revealed that ygl1 encodes the tandem 13-LOX genes in a cluster. Four missense mutations were found in four tandem 13-LOX genes (Csa4M286960, Csa4M287550, Csa4M288070, and Csa4M288080) in the ygl1 mutant, and the four 13-LOX genes showed high similarity with one another. The transient RNA interference and virus-induced gene silencing of these genes simultaneously resulted in yellow-green leaves with a reduced amount of chloroplasts and increased relative carotenoid content, which were observed in the ygl1 mutant. This evidence supported the non-synonymous SNPs (Single Nucleotide Polymorphism) in the four tandem 13-LOX genes as being the causative mutation for the yellow-green leaves. Furthermore, this study provides a new allele for breeding cucumbers with yellow-green leaves and serves as an additional resource for studying carotenoid biosynthesis.

Comprehensive Genomic Characterization and Expression Analysis of the Lipoxygenase Gene Family in Watermelon under Hormonal Treatments

“…Moreover, over half of the ClLOX genes (10 in 16) were identified as tandemly duplicated genes, indicating that tandem duplication events are the main driving force for the evolution of ClLOX genes. This feature has also been found in some other plants, such as poplar [11], maize [16], tomato [18], cucumber [34], and radish [15]. In addition, according to the collinear module of watermelon and Arabidopsis, all of the six AtLOX genes have syntenic copies in ClLOX genes (Supplementary Figure S3).…”

Fine Mapping and Transcriptome Analysis of Virescent Leaf Gene v-2 in Cucumber (Cucumis sativus L.)

“…As compared with the normal green plants, 9110Gt and vyl mutant could grow up to the same or slightly smaller plant height. The ygl1 mutant was a spontaneous mutant isolated from inbred cucumber 1402, which was slightly smaller than the wild type throughout the developmental stage ( Ding et al, 2019 ). The C777 mutant displayed yellow color in cotyledons and true leaves with stay-green dots at emergence.…”

“…The virescent leaf trait had also been reported to be controlled by one single recessive nuclear gene in some other plants, such as Arabidopsis thaliana ( Ma et al, 2017 ; Huang et al, 2018 ), rice ( Wang et al, 2016 ; Zhu et al, 2016 ), cotton ( Zhu et al, 2017 ; Mao et al, 2019 ), maize ( Xing et al, 2014 ), cabbage ( Liu et al, 2016 ), apple ( Fernández-Fernández et al, 2014 ), watermelon ( Zhang et al, 1996 ) and so on. In cucumber, the virescent traits in 9110Gt ( Miao et al, 2016 ), vyl mutant ( Song et al, 2018 ), ygl1 ( Ding et al, 2019 ) and C777 ( Hu et al, 2020 ) were also controlled by one single recessive nuclear gene. It indicated that the virescent mutants were easy to form because the mutation of anyone gene involving in the pathways of chloroplast development or chlorophyll biosynthesis could generate the virescent leaf appearance ( Beale, 2005 ).…”

“…Cucumber, Cucumis sativus L. (2n = 2x =14), is a popular vegetable crop around the world. Although 17 leaf color mutants including light green cotyledons-1 (lg-1), light green cotyledons-2 (lg-2), yellow cotyledons-1 (yc-1), yellow cotyledons-2 (yc-2), golden leaf (g), virescent (v), virescent-1 (v-1), variegated virescent (vvi), yellow plant (yp), yellow-green leaf (yg1), virescent-yellow leaf (vyl), yellow young leaf-1 (yyl-1), chlorophyll deficient (cd), golden cotyledon (gc), albino cotyledon (al), light sensitive (ls) and pale lethal (pl) (Weng and Wehner, 2017;Song et al, 2018;Ding et al, 2019;Hu et al, 2020) have been identified in cucumber, however, limited work has been conducted on genetic mapping of these leaf color mutant genes or elucidating their regulation mechanisms. Up to date, only five leaf color mutant genes have been map-based cloned.…”

“… Song et al (2018) reported a virescent-yellow leaf ( vyl ) mutant derived from an EMS-mutagenized, and confirmed that gene Csa4G637110 on chromosome 4 was the most likely candidate gene for vyl . Ding et al (2019) reported that the formation of ygl mutant in cucumber was caused by the mutation of tandem 13-lipoxygenase ( 13-LOX ) genes in a cluster. Hu et al (2020) revealed that a mutation in CsHD encoding a histidine and aspartic acid domain containing protein leaded to the formation of yyl-1 mutant in cucumber.…”