Abstract
Arabidopsis acaulis1 (acl1) was isolated as a mutant having defects in the elongation of inflorescence stem. Also, it has small curled leaves. acl1 phenotype can be altered by two environmental factors. It is repressed when plants are grown at temperatures higher than 26C. And plant size of acl1 mutants depends on nitrogen condition in growth media.
Some temperature-dependent phenotypes similar to acl1 are reported to be triggered by the activation of salicylic acid mediated defense pathways against pathogens. We found that expression levels of defense genes in acl1 were high in the conditions which acl1 plants exhibit severe growth defects. At higher temperatures or on altered nitrogen conditions, those levels were relatively low. Depression of defense gene was stronger on the conditions that allow acl1 phenotype to be repressed more complete. Moreover, acl1 phenotype was suppressed by mutations in PAD4 gene which play key roles in defense pathway. These results indicate that temperature- and nitrogen condition-dependent phenotype caused by acl1 mutation requires function and activation of genetic defense pathways, which are regulated by temperature and nitrogen conditions.
