Abstract
In bacterial cells, RelA/SpoT catalyzes synthesis or degradation of guanosine 3',5'-bispyrophosphate (ppGpp) in response to environmental stresses such as amino acid starvation. ppGpp controls transcription of a large number of genes through direct interaction with RNA polymerase. This process which regulates gene expression is called stringent response. Recently a growing number of RelA/SpoT homologues, designated RSH, has been identified in plants. To reveal the role of stringent response in plant cells, we are investigating four RSHs (RSH1,2,3 and CRSH) in Arabidopsis.
As a result of promoter analysis, the four RSH genes of Arabidopsis were shown to express in green tissues and flowers. In addition, Arabidopsis CRSH knockdown mutant had defects in reproduction stage, which implies the involvement of the CRSH in seed formation. Besides, we observed induction of RSH2 mRNA expression in response to abiotic stresses. These results show that stringent response has an important role in higher plants' physiology.
