RESUMO
Ascorbate peroxidase (APX) is an important reactive oxygen species (ROS)-scavenging enzyme, which catalyzes the removal of hydrogen peroxide (H2O2) to prevent oxidative damage. The peroxidase activity of APX is regulated by posttranslational modifications (PTMs), such as S-nitrosylation, tyrosine nitration, and S-sulfhydration. In addition, it has been recently reported that APX functions as a molecular chaperone, protecting rice against heat stress. In this study, we attempted to identify the various functions of APX in Arabidopsis and the effects of PTMs on these functions. Cytosol type APX1 from Arabidopsis thaliana (AtAPX1) exists in multimeric forms ranging from dimeric to high-molecular-weight (HMW) complexes. Similar to the rice APX2, AtAPX1 plays a dual role behaving both as a regular peroxidase and a chaperone molecule. The dual activity of AtAPX1 was strongly related to its structural status. The main dimeric form of the AtAPX1 protein showed the highest peroxidase activity, whereas the HMW form exhibited the highest chaperone activity. Moreover, in vivo studies indicated that the structure of AtAPX1 was regulated by heat and salt stresses, with both involved in the association and dissociation of complexes, respectively. Additionally, we investigated the effects of S-nitrosylation, S-sulfhydration, and tyrosine nitration on the protein structure and functions using gel analysis and enzymatic activity assays. S-nitrosylation and S-sulfhydration positively regulated the peroxidase activity, whereas tyrosine nitration had a negative impact. However, no effects were observed on the chaperone function and the oligomeric status of AtAPX1. Our results will facilitate the understanding of the role and regulation of APX under abiotic stress and posttranslational modifications.
RESUMO
Low productivity of pilosae type lentils grown in South Asia is attributed to narrow genetic base of the released cultivars which results in susceptibility to biotic and abiotic stresses. For enhancement of productivity and production, broadening of genetic base is essentially required. The genetic base of released cultivars can be broadened by using diverse types including bold seeded and early maturing lentils from Mediterranean region and related wild species. Genetic diversity in eighty six accessions of three species of genus Lens was assessed based on twelve genomic and thirty one EST-SSR markers. The evaluated set of genotypes included diverse lentil varieties and advanced breeding lines from Indian programme, two early maturing ICARDA lines and five related wild subspecies/species endemic to the Mediterranean region. Genomic SSRs exhibited higher polymorphism in comparison to EST SSRs. GLLC 598 produced 5 alleles with highest gene diversity value of 0.80. Among the studied subspecies/species 43 SSRs detected maximum number of alleles in L. orientalis. Based on Nei's genetic distance cultivated lentil L. culinaris subsp. culinaris was found to be close to its wild progenitor L. culinaris subsp. orientalis. The Prichard's structure of 86 genotypes distinguished different subspecies/species. Higher variability was recorded among individuals within population than among populations.
