A fragment substitution in the promoter of CsHDZIV11/CsGL3 is responsible for fruit spine density in cucumber (Cucumis sativus L.)

Abstract

The indel in the promoter of CsHDZIV11 co-segregates with fruit spine density and could be used for molecular breeding in cucumber. Fruit spine density is an important quality trait for marketing in cucumber (Cucumis sativus L.). However, the molecular basis of fruit spine density in cucumber remains unclear. In this study, we isolated a mutant, few spines 1 (fs1), from CNS2 (wild type, WT), a North China-type cucumber with a high density of fruit spines. Genetic analysis showed that fs1 was controlled by a single recessive Mendelian factor. Bulked segregant analysis combined with genome resequencing were used for mapping fs1 in the F2 population derived from a cross between the fs1 mutant and WT, and it was located on chromosome 6 through association analysis. To develop more polymorphic markers to locate fs1, another F2 population was constructed from the cross between fs1 and 'Chinese long' 9930. Then, fs1 was narrowed down to a 110.4-kb genomic region containing 25 annotated genes. A fragment substitution was identified in the promoter region of Csa6M514870 between fs1 and WT. This fragment in fs1 was also present in wild cucumber. Csa6M514870 encodes a PDF2-related protein, a homeodomain-leucine zipper IV transcription factor (CsHDZIV11/CsGL3) sharing high identity and similarity with proteins related to trichome formation or epidermal cell differentiation. Quantitative reverse-transcription PCR revealed a higher expression level of CsHDZIV11 in young fruits from fs1 compared to WT. A molecular marker based on this indel co-segregated with the spine density. This work provides a solid foundation not only for understanding the molecular mechanism of fruit spine density, but also for molecular breeding in cucumber.

Perspectives of CRISPR/Cas-mediated cis-engineering in horticulture: unlocking the neglected potential for crop improvement

“…Another example from apple is that a 36-bp insertion in MdSAUR37 promoter contributed to high fruit malate content 39 . In cucumber (Cucumis sativus L.), a 10-bp fragment was replaced by an 812-bp fragment in the promoter of CsHDZIV11/CsGL3 at the few spines 1 (fs1) locus, giving rise to higher expression of CsGL3 and fewer fruit spines 40 .…”

Classification of fruit trichomes in cucumber and effects of plant hormones on type II fruit trichome development

“…mict, tbh), csgl2, and csgl3 (syn. tril), and the respective genes play important roles in trichome initiation or development (Yang et al 2011;Chen et al 2014;Li et al 2015;Zhao et al 2015;Pan et al 2015;Cui et al 2016;Liu et al 2016;Wang et al 2016;Zhang et al 2016;). However, a systematic investigation of fruit trichomes is lacking.…”

CsMYB60is a key regulator of flavonols and proanthocyanidans that determine the colour of fruit spines in cucumber

“…We compared the sequences of the two CsMYB60 alleles from the inbred lines RNS8 (white spines) and RNS9 (black spines), and found a 6994-bp insertion at the 1492-bp position after the transcription start site in the second intron of CsMYB60 in RNS8 compared with RNS9. To determine whether this R2R3-MYB gene was conserved in different varieties, we tested 20 other cucumber inbred lines from different geographical regions that were available in our laboratory (Zhang et al , 2016); 14 of the 22 lines have white spines and eight have black spines. The results of the sequencing analysis indicated that the CsMYB60 alleles from the lines with black spines (CNS14, CNS20, RNS5, RNS12, and RNS13) had the same genomic sequence as that in RNS9.…”