Regulatory function of AMP1 in ABA biosynthesis and drought resistance in arabidopsis

In this study we reported the isolation of a mutant in which the reporter pVP14-LUC was highly expressed in Arabidopsis. The gene expression of maize VP14 is closely correlated with the endogenous ABA levels, and the Arabidopsis homolog of VP14, AtNCED1, encoding an enzyme of ABA biosynthesis, was up-regulated, and high ABA level was detected in the mutant. Map-based cloning revealed that the mutated gene is a novel allele of the AMP1 (Altered Meristem Program 1) which encodes a glutamate carboxypeptidase that plays an important role in shoot apical meristem development and phytohormone homeostasis. We found that the mutant displayed obvious drought tolerance, being with more lateral roots, high seed germination under mannitol, increased ABA accumulation, and highly induced gene expression of RD29A. Using the approaches of artificial microRNA gene silencing in transgenic plants, three AMP1 down-regulated lines were obtained. The AMP1 down-regulated plants exhibited a low rate of water loss, decreased stomatal aperture, and enhanced drought tolerance. These results provide evidence demonstrating the regulatory function of AMP1 in plant drought tolerance and stress responsive gene expression.