Proteomic and Biochemical Analyses Show a Functional Network of Proteins Involved in Antioxidant Defense of the <i>Arabidopsis</i> <i>anp2anp3</i> Double Mutant

Disentanglement of functional complexity associated with plant mitogen-activated protein kinase (MAPK) signaling has benefited from transcriptomic, proteomic, phosphoproteomic, and genetic studies. Published transcriptomic analysis of a double homozygous recessive <i>anp2anp3</i> mutant of two MAPK kinase kinase (MAPKKK) genes called <i><u>A</u>rabidopsis thaliana Homologues of <u>N</u>ucleus- and <u>P</u>hragmoplast-localized Kinase 2</i> (<i>ANP2</i>) and 3 (<i>ANP3</i>) showed the upregulation of stress-related genes. In this study, a comparative proteomic analysis of <i>anp2anp3</i> mutant against its respective Wassilevskaja ecotype (Ws) wild type background is provided. Such differential proteomic analysis revealed overabundance of core enzymes such as FeSOD1, MnSOD, DHAR1, and FeSOD1-associated regulatory protein CPN20, which are involved in the detoxification of reactive oxygen species in the <i>anp2anp3</i> mutant. The proteomic results were validated at the level of single protein abundance by Western blot analyses and by quantitative biochemical determination of antioxidant enzymatic activities. Finally, the functional network of proteins involved in antioxidant defense in the <i>anp2anp3</i> mutant was physiologically linked with the increased resistance of mutant seedlings against paraquat treatment.