Effects of Endogenous Hormones on Variation of Shoot Branching in a Variety of Non-heading Chinese Cabbage and Related Gene Expression

다국어 초록 (Multilingual Abstract)

Shoot branching (tillering) primarily determinesplant shoot architecture and has been studied in many plants.
Shoot branching is an important trait in non-heading Chinesecabbage (Brassica rapa ssp. chinensis Makino). The B. rapassp. chinensis var. multiceps exhibits unique and multipleshoot branching characteristics. Here, we analyzed the variationin shoot branching between ‘Maertou,’ with multiple shootbranching, and ‘Suzhouqing,’ a common variety. The levelsof endogenous indole-3-acetic acid (IAA), zeatin ribosideand active gibberellins in the shoot meristem tissues of thetwo cultivars were quantified by enzyme-linked immunosorbentassay during the vegetative growth stage. High levels of IAAmaintained axillary bud dormancy and repressed axillary budoutgrowth allowing shoot branching to form in the vegetativestage in ‘Suzhouqing.’ In contrast, low levels of IAA did notinhibit axillary buds in ‘Maertou,’ while a high level of cytokininpromoted axillary bud growth and branch shoot development.
Exogenous hormone (rac-GR24 and 6-benzylaminopurine)treatment showed that ‘Maertou’ was relatively sensitive tocytokinin, because the fold changes of cytokinin-responsivegenes in ‘Maertou’ were significantly more frequent than thosein ‘Suzhouqing’. Cytokinin was the direct regulator for axillarybud growth of ‘Maertou’. Compared with ‘Suzhouqing’,‘Maertou’ was sensitive to cytokinin and this weakened thestrigolactone–cytokinin branching pathway.

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