Ectopic Expression Analysis Of MhGAI2 In Tomato

The phytohormone gibberellic acid (GA) regulates plant growth and development in various aspects such as seed germination, hypocotyl elongation, leaf expansion and flowering time, In plants, GA responses are repressed by DELLA proteins, which contain an N-terminal DELLA domain essential for GA-dependent proteasomal degradation of DELLA repressors. Mutations of or within the DELLA domain have been showed that the mutation confer GA insensitivity and constrain the growth of plants.MhGAI2 gene isolated from tea crabapple (Malus hupehensis) encoded a predicated DELLA protein.ΔMhGAI2 was its GA-insensitive allele artificially obtained with a bridge-PCR approach. Ectopic expression analysis in tomato verified that that its GA-insensitive alleleΔMhGAI2 caused dwarfism. Transgenic tomato lines TH and TL ectopically expressedΔMhGAI2 transcripts at high and low levels, respectively , Because TH and TL homozygous plants exhibited extremely GA-insensitive dwarfism and sterility, semi-dwarf heterozygous progenies were used to examine ifΔMhGAI2 alters growth habits. Meanwhile, the transgenic tomato pBI containing pBI121 empty vector was used as control.Transgenic plants showed only a slight growth response to GA3. Genetic analysis indicates thatΔMhGAI2 is a mutant repressor that is relatively resistant to the effects of GA, which exhibited shorter internodes in primary and branch shoots and smaller plant statures than pBI. Interestingly, Transgenic plants also generated compacted inflorescences with small flowers, resulting in small fruits and seeds relative to pBI. In addition, transgenic seedlings were more resistant to drought stress than pBI.