Twining growth habit is a beneficial phenotype in many wild plants, but in mass cultivation, these crops need more of manpower and facilities than the erect growth habit. However, little is known about the molecular mechanism involved in formation of ...
Twining growth habit is a beneficial phenotype in many wild plants, but in mass cultivation, these crops need more of manpower and facilities than the erect growth habit. However, little is known about the molecular mechanism involved in formation of vine growth habit. Therefore, this study used mapping and genomic diversity analysis to identify genetic factors related to twining growth habit in soybean. Soybean is domesticated from its wild progenitor Glycine soja. Wild soybean has both creeping nature and vines that climb on supports, while most cultivated soybean grows erect and straight. Taking the advantages of growth habit difference between wild and cultivated soybeans, F2 populations were obtained by hybridizing wild and cultivated soybeans. To find the candidate gene, we considered the presence of vines and plant height on support system in the F2 population. QTL analysis revealed that one major region in chromosome 19. Further, the QTL region was physical mapping to a 0.65 Mb from physical position 44,925,947 to 45,581,180 on chromosome 19. The 0.65 Mb region is composed of 58 predicted genes. Among them, a gene with BTB/POZ domain is considered as major candidate for the vine growth habit by considering SNP and Indel data of wild and cultivated soybeans. On the other hand, to investigate the molecular mechanism of stem coiling in Arabidopsis, a screening was carried out from T-DNA inserted activation tagging lines. A mutant with a wavy and curly morphology, and coiling branches, named cbr1, was identified. Plasmid rescue and genomic southern blot analysis confirmed the site of T-DNA insertion in the genome. RT-PCR was performed to monitor expression levels of the genes adjacent to the T-DNA integration site and showed the activation of an E3 ubiquitin ligase gene. Database search revealed that the protein with the C3HC4 type RING domain belongs to a family of E3 ubiquitin ligases. Complementation test by overexpression and RNA interference of the gene showed that activation of the novel gene caused the cbr1 mutant phenotypes. E3 ubiquitin ligase has been reported to recognize target proteins that are needing to be ubiquinated for further degradation by the proteasome complex. Further, eight candidate target substrates for E3 ubiquitin ligase were obtained by performing a yeast two-hybrid screening. To examine whether eight candidate target proteins interact with CBR1 in vivo. Eight candidate target proteins were co-overexpressed in cbr1 mutant plants. As a result, overexpression of the three putative target genes in cbr1 mutant leads to recovery of wild type. These findings indicate that the three candidate target proteins might be the major factors influenced by CBR1 E3 ubiquitin ligase to cause the cbr1 phenotype.