The glutamate carboxypeptidase AMP1 mediates abscisic acid and abiotic stress responses in Arabidopsis

Abstract

SummaryALTERED MERISTEM PROGRAM1 (AMP1) encodes a glutamate carboxypeptidase that plays an important role in shoot apical meristem development and phytohormone homeostasis.We isolated a new mutant allele of AMP1, amp1-20, from a screen for abscisic acid (ABA) hypersensitive mutants and characterized the function of AMP1 in plant stress responses.amp1 mutants displayed ABA hypersensitivity, while overexpression of AMP1 caused ABA insensitivity. Moreover, endogenous ABA concentration was increased in amp1-20-and decreased in AMP1-overexpressing plants under stress conditions. Application of ABA reduced the AMP1 protein level in plants. Interestingly, amp1 mutants accumulated excess superoxide and displayed hypersensitivity to oxidative stress. The hypersensitivity of amp1 to ABA and oxidative stress was partially rescued by reactive oxygen species (ROS) scavenging agent. Furthermore, amp1 was tolerant to freezing and drought stress. The ABA hypersensitivity and freezing tolerance of amp1 was dependent on ABA signaling. Moreover, amp1 had elevated soluble sugar content and showed hypersensitivity to high concentrations of sugar. By contrast, the contents of amino acids were changed in amp1 mutant compared to the wild-type.This study suggests that AMP1 modulates ABA, oxidative and abotic stress responses, and is involved in carbon and amino acid metabolism in Arabidopsis.

ALTERED MERISTEM PROGRAM1Suppresses Ectopic Stem Cell Niche Formation in the Shoot Apical Meristem in a Largely Cytokinin-Independent Manner

“…In this light, the increase in CK levels in amp1 appears to be a secondary effect and affects SAM phenotypes only slightly. This is in strong contrast to the traditional view that most of the SAM defects are CK related but consistent with later findings that amp1 also shows alterations in abscisic acid, GA, and ethylene responses (Saibo et al, 2007;Shi et al, 2013aShi et al, , 2013bYao et al, 2014). However, based on the current knowledge, it is also difficult to coherently attribute the SAM syndrome of amp1 solely to altered activities in one of these hormonal pathways.…”

“…For example, amp1 alleles show alterations in seed dormancy and timing of phase transitions as well as a strongly enhanced leaf formation rate (Chaudhury et al, 1993;Conway and Poethig, 1997;Telfer et al, 1997;Griffiths et al, 2011). Other hormone pathways are also affected in amp1, including GA, ethylene, and abscisic acid, and AMP1 absence abrogates the requirement of the auxindependent transcription factor AUXIN RESPONSE FACTOR5 in the process of embryonic root formation (Saibo et al, 2007;Vidaurre et al, 2007;Shi et al, 2013aShi et al, , 2013bYao et al, 2014). Recently, it has been shown that the translation rate of micro-RNA (miRNA)-controlled proteins in amp1 is specifically enhanced at endoplasmic reticulum (ER)-located polysomes by an unknown mechanism, suggesting that at least some of the amp1 phenotypes might be caused by deregulated activity of miRNA-controlled pathways (Li et al, 2013).…”

Insights from the Cold Transcriptome and Metabolome of Dendrobium officinale: Global Reprogramming of Metabolic and Gene Regulation Networks during Cold Acclimation

“…The catabolism of Ile, leu, Val and progressive conversion of organic acids in TCA with intial help of acetyl-CoA results in the production of high energy carriers (such as NADH, FADH2, and GTP). Such a process has been widely observed during CA and other stress conditions (Kaplan et al, 2007; Jozefczuk et al, 2010; Shi et al, 2013). Our results showed that the accumulation of several important intermediaries such as citratic acid, succinic acid and fumaric acid in TCA were responsible for the activation of multiple enzymes encoding isocitrate lyase (ICL), aconitate hydratase (ACO) and succinate dehydrogenase (SDH), which were more than two fold up-regulation during CA, especially ICL that was six fold up-regulated.…”

Transcriptome Analysis Reveals Crosstalk of Responsive Genes to Multiple Abiotic Stresses in Cotton (Gossypium hirsutum L.)

“…The 60S ribosomal protein L4A can be directly regulated by auxin and the exogenous application of auxin results in vacuolar trafficking defects of plants [62,63]. The carboxypeptidase is functional in post-translational modification [64,65] and the leucine-rich repeat-containing protein are involved in the formation of protein-protein interaction and signaling [66]. …”