ALTERED MERISTEM PROGRAM 1 Plays a Role in Seed Coat Development,Root Growth,and Post-Embryonic Epidermal Cell Elongation in Arabidopsis

Plant development relies on the capacity of cells to interpret positional information and translate it into proliferation, elongation, and differentiation programs. ALTERED MERISTEM PROGRAM 1 (AMP1) encodes a putative glutamate carboxypeptidase involved in embryo development, plant growth, and phytohormone homeostasis. Here, we show that mutations of AMP1 cause defective seed coat formation, which correlates with increased frequency of embryo abortion, low seed production, and retarded germination. Seed alterations in amp1 mutants were related to decreased production of trichomes on leaves and increased ratio of short or bifurcated root hairs in primary roots and primary root growth inhibition. Expression analyses of hormone-related gene constructs TCS::GFP, DR5:uidA, and pABI4:uidA indicated that slow root growth is likely independent of cytokinin and auxin signaling and involves changes in abscisic acid responsiveness. Our data show that AMP1 is necessary for normal seed coat and embryo establishment during seed development and plays an important role in post-embryonic root growth and epidermal cell elongation.