Fine mapping and candidate gene analysis of the virescent gene v 1 in Upland cotton (Gossypium hirsutum)

Abstract

The young leaves of virescent mutants are yellowish and gradually turn green as the plants reach maturity. Understanding the genetic basis of virescent mutants can aid research of the regulatory mechanisms underlying chloroplast development and chlorophyll biosynthesis, as well as contribute to the application of virescent traits in crop breeding. In this study, fine mapping was employed, and a recessive gene (v ) from a virescent mutant of Upland cotton was narrowed to an 84.1-Kb region containing ten candidate genes. The GhChlI gene encodes the cotton Mg-chelatase I subunit (CHLI) and was identified as the candidate gene for the virescent mutation using gene annotation. BLAST analysis showed that the GhChlI gene has two copies, Gh_A10G0282 and Gh_D10G0283. Sequence analysis indicated that the coding region (CDS) of GhChlI is 1269 bp in length, with three predicted exons and one non-synonymous nucleotide mutation (G1082A) in the third exon of Gh_D10G0283, with an amino acid (AA) substitution of arginine (R) to lysine (K). GhChlI-silenced TM-1 plants exhibited a lower GhChlI expression level, a lower chlorophyll content, and the virescent phenotype. Analysis of upstream regulatory elements and expression levels of GhChlI showed that the expression quantity of GhChlI may be normal, and with the development of the true leaf, the increase in the Gh_A10G0282 dosage may partially make up for the deficiency of Gh_D10G0283 in the v mutant. Phylogenetic analysis and sequence alignment revealed that the protein sequence encoded by the third exon of GhChlI is highly conserved across diverse plant species, in which AA substitutions among the completely conserved residues frequently result in changes in leaf color in various species. These results suggest that the mutation (G1082A) within the GhChlI gene may cause a functional defect of the GhCHLI subunit and thus the virescent phenotype in the v mutant. The GhChlI mutation not only provides a tool for understanding the associations of CHLI protein function and the chlorophyll biosynthesis pathway but also has implications for cotton breeding.

The Cotton BEL1-Like Transcription Factor GhBLH7-D06 Negatively Regulates the Defense Response against Verticillium dahliae

“…Agrobacterium strains containing TRV1 and Agrobacterium strains containing TRV: GhBLH7-D06 or TRV: 00 were mixed in equal amounts and infiltrated into the cotyledons of 10-day-old “TM-1” seedlings by syringe infiltration to generate the control (TRV: 00 ) and GhBLH7-D06 -silenced (TRV: GhBLH7-D06 ) cotton. TRV: CHLI ( Magnesium-chelatase subunit I ) was used as a positive control as previously described [ 58 ]. Because the etiolated leaf phenotype appeared in the TRV: CHLI plants at 10 days after infiltration, we selected that as the time to inoculate the seedlings with Vd991-GFP and to take samples for calculating the silencing efficiency.…”

Map-based cloning of a recessive gene v1 for virescent leaf expression in cotton (Gossypium spp.)

“…We hypothesized that the different phenotype of the virescent-1 mutant in T582 compared with normal plant in 3-79 is probably due to the promoter difference between them (Zhu et al 2017;Mao et al 2018).…”

Prospects for Molecular Breeding in Cotton,Gossypiumspp

“…Transfer of QTL/pyramiding of QTLs is one way of realizing targeted trait introgression [120] or these QTLS can be utilized for fine mapping and map-based cloning before markerassisted selection. However, only a few validation studies are done for the Virescent gene in Virescent mutants [121,122], the fuzzless gene in the fuzzless mutant [123], traits like fiber length [124], Fiber strength [125], leaf shape [126] and QTL affecting root-knot nematode multiplication [127] etc. Though fine-mapping is done it would require still more concentrated efforts to dissect out the traits.…”