Effects of gibberellin mutations on in vitro shoot bud regeneration of Arabidopsis

Tissue culture provides a useful system to investigate how plant hormones are involved in this process. Auxin and cytokinin are widely used in plant regeneration. Gibberellin is also an important plant hormone in regulating plant growth and development. It is interesting to know the effects of gibberellin and its signalling pathway on plant regeneration. In this report Arabidopsis thaliana landsberg (wild type), ga1-3 (gibberellin biosynthesis deficiency mutant), gai (gibberellin insensitive mutant), penta mutant (lacking GA1, GAI, RGA, RGL1, RGL2) and tetra mutant (lacking GAI, RGA, RGL1, RGL2) were used as materials to investigate how plant regeneration progress was affected in these mutants under different conditions. The results showed that more shoot buds were regenerated in ga1-3 and gai than in wild type, penta and tetra mutant in the normal shoot induction medium. The frequency of shoot bud regeneration in different mutants also varied remarkably when auxin : cytokinin ratio in the medium changed. Only penta mutant had shoot bud regeneration without auxin in the medium. When the ratio increased wild type, ga1-3 and gai had higher performance in shoot bud regeneration than penta mutant. When cytokinin level increased from 0.1 to 0.5 mg l, shoot bud regeneration frequency of ga1-3, wild type and tetra increased remarkably except for that of penta and gai. Only the shoot bud regeneration frequency of gai did not change significantly when cytokinin level increased from 0.5 to 5 mg l. These gibberellin-related mutants also responded differently to NPA (an auxin polar transport inhibitor) in plant regeneration. Our results indicate gibberellin and its related pathway are also involved in plant organogenesis: gibberellin inhibitor and auxin polar transport inhibitor can promote plant organogenesis. This might provide a new way for the regeneration of recalcitrant species.