Abstract
We have already reported that chlorophyll contents in cucumber plants increased by the application of ABA under low nitrogen conditions. In this study, we investigated the regulation of gene expression for synthesis and degradation of chlorophyll in cucumber plants under low nitrogen conditions by semi-quantitative RT-PCR. The amount of transcripts of genes for chlorophyll biosynthesis, glutamyl-tRNA reductase (GR), Mg chelatase D subunit (Mg-D) and Mg chelatase H subunit (Mg-H), reduced in older cucumber plants grown without ABA. The levels of transcripts of genes for chlorophyll degradation, chlorophyll b reductase (NYC), pheophytinase (PPH), pheophorbide a oxygenase (PAO) and red chlorophyll catabolite reductase (RCCR), increased in older plants without ABA. On the other hand, the levels of transcripts of genes for chlorophyll synthesis were almost same in cucumber plants cultivated for 10 and 20 days in presence of ABA 10-5M. The amounts of transcripts of genes for chlorophyll degradation in cucumber plants with ABA 10-5M were smaller than that in drug free plants. These results suggest that ABA promotes chlorophyll biosynthesis and suppress chlorophyll degradation in cucumber plants under low nitrogen conditions.
