The Map-based Cloning Of Hpa1 And The Functional Analysis Of HPA

Histidine, an essential ingredient for protein synthesis, is required by all living organisms. In higher plants, although considerable evidence shows that histidine is essential for plant growth and survival, little information regarding whether it plays any specific regulatory role in plant development is available. Here we present evidence for the regulatory role of histidine in Arabidopsis. A novel Arabidopsis mutant, hpa1, was selected because of its remarkable short primary root length. Using map-based cloning method, it is found that the mutated phenotype was caused by disturbing of one of the two Arabidopsis histidinol phosphate aminotransferase (HPA) genes. Biochemical analysis shows that this mutant has reduced free histidine content. Although the mutant did not show significant symptoms of histidine starvation, it displayed a dramatic developmental defect in root, i.e. unable to maintain root meristems. Our data showed that the defects in the mutant were related to the shift of the free histidine content in mutant plant. The mutant phenotype could be rescued either by exogenous histidine supplementation or complemented by HPA over-expression. Our results reveal that histidine homeostasis plays important roles in plant development.