Abstract:

To examine the gene-gene interactions between GA20ox1 and rol gene so as to elucidate the molecular mechanism of dwarfing morphogenesis in citrange. The potted seedlings of transgenic citrange with rol ABC genes were used as trial materials, the sensitive response to GAs was tested by spraying GA3 regularly, the expression of GA20ox1 and rol A, B and C genes were detected by quantitative reverse transcription PCR, phytohormone content of tender bud were quantified by GC/MS method. The result demonstrated transgenic citrange was neither defective genotype of GA3, nor unsensitive genotype of GA3. However, the spraying of GA3 elongated the internode; it was still shorter than wild type citrange. The content of IAA (P<0.01), GA1 and GA4 decreased (P<0.05) while peroxidase activity increased markedly in the tender bud of transgenic citrange (P<0.01). The GA20ox1 expression quantity markedly decreased in apical bud (P<0.01), while it was similar in tender stem of B, D clones, and decreased in old leaves, compared with that in wild type. However, the expression in tender stem and old leaves were increased. Also its expression in tender leaves was higher than wild type. The expression of rol C gene and GA20ox1 gene reveal negative correlation in tender bud, tender stems. rol gene expression could inhibit synthesis of GAs by down regulating the expression of GA20ox1 gene in bud, lower bioactive GAs could suppress citrange growth, then it played an important role in constructing dwarfing characteristics of transgenic citrange with rol ABC genes.