A mutation in CsHY2 encoding a phytochromobilin (PΦB) synthase leads to an elongated hypocotyl 1(elh1) phenotype in cucumber (Cucumis sativus L.)

Abstract

Hypocotyl length is a critical determinant in establishing high quality seedlings for successful cucumber production, but knowledge on the molecular regulation of hypocotyl growth in cucumber is very limited. Here we reported identi cation and characterization of a cucumber elongated hypocotyl 1 (elh1) mutant. We found that the longer hypocotyl in elh1 was due to longitudinal growth of hypocotyl cells. With ne mapping, the elh1 locus was delimited to a 20.9-kb region containing three annotated genes; only one polymorphism was identi ed in this region between two parental lines, which was a non-synonymous SNP (G28153633A) in the third exon of CsHY2 (CsGy1G030000) that encodes a phytochromobilin (PΦB) synthase. Uniqueness of the mutant allele at CsHY2 was veri ed in 515 cucumber lines. Ectopic expression of CsHY2 in Arabidopsis hy2-1 mutant led to reduced hypocotyl length. The PΦB protein was targeted to chloroplasts. The expression levels of CsHY2 and ve phytochrome genes, CsPHYA1, CsPHYA2, CsPHYB, CsPHYC and CsPHYE were all signi cantly down-regulated while several cell elongation related genes were up-regulated in elh1 mutant compared to wild type cucumber, which are correlated with dynamic hypocotyl elongation in the mutant. RNA-seq analysis in the WT and mutant revealed differentially expressed genes involved in porphyrin and chlorophyll metabolisms, cell elongation, and plant hormone signal transduction pathways. This is the rst report to characterize and clone the CsHY2 gene in cucumber. This work reveals the important of CsHY2 in regulating hypocotyl length and extends our understanding of the roles of CsHY2 in cucumber.

Integrated Transcriptome and Proteome Analysis Revealed the Regulatory Mechanism of Hypocotyl Elongation in Pakchoi

“…Similar results were observed in a long hypocotyl mutant of Arabidopsis [ 27 ]. Previous studies have also shown that the hypocotyl elongation rate in the long hypocotyl mutant elh1 was significantly higher than that of the short hypocotyl WT at any time point in cucumber [ 28 ]. Studies of long-hypocotyl mutants, such as lhy7.1 , may provide a theoretical basis for the breeding of long-hypocotyl varieties which could be applied in mechanized production.…”

“…Cell elongation, rather than cell division, largely contributes to hypocotyl growth [ 29 , 30 ]. Previous studies have shown that hypocotyl growth mainly depends on cell longitudinal elongation in Arabidopsis and cucumber [ 5 , 6 , 28 , 29 ]. We examined the length of the hypocotyl cells of both WT and lhy7.1 grown in an artificial climate box under controlled environmental conditions using semi-thin sections.…”

“…SAUR10 , SAUR19 , SAUR50 , and SAUR 64 were up-regulated [ 42 ]. Moreover, in cucumber, DEGs between a longer hypocotyl mutant and WT were annotated to “photosynthesis” and “phytohormone signal transduction” pathways [ 28 ]. These results supported our results that hypocotyl elongation may be due to the changes in photosynthesis and auxin pathways, indicating that the molecular mechanism of hypocotyl elongation may be conserved in higher plants.…”

Integrated proteomics and metabolomics analysis reveals the pathways of red light regulating soybean hypocotyl elongation and thickening

“…Hypocotyl is an ideal model for studying the response of plant stem to light exposure due to its high sensitivity to light signals (Falcioni et al, 2019;Samimy, 1978;Kato-Noguchi & Kasai, 1991;Mazzella et al, 1997;Boron & Vissenberg, 2014;Hu et al, 2021). Proteomics and metabolomics are effective tools for identifying DEPs, DEMs, and related pathways (Li et al, 2018;Wei et al, 2020;Mirzahosseini et al, 2020;Liu et al, 2019;Fan et al, 2018;Yates et al, 2009;Ryan & Robards, 2006).…”

A Novel 10-Base Pair Deletion in the First Exon of GmHY2a Promotes Hypocotyl Elongation, Induces Early Maturation, and Impairs Photosynthetic Performance in Soybean

“…Kohchi et al (2001) initially reported the long-hypocotyl mutation of the HY2 gene encoding PΦB synthetase in Arabidopsis [10]. Subsequently, abnormal PΦB synthase function was reported in various other species, including the pcd2 mutant in pea (Pisum sativum L.) [11], the se13 mutant in rice (Oryza sativa L.) [12], the elh1 mutant in cucumber (Cucumis sativus L.) [13], the Gmlin1 mutant in soybean [14], and the Mtpφbs mutant in alfalfa (Medicago truncatula) [15]. Studies have shown that chromophore-deficient mutants generally have a light green or yellowish leaf phenotype, accompanied by a reduction in chlorophyll.…”