Radical-induced cell death1 and similar to RCD one1 and the stress-induced morphogenetic response

Abstract

Plants exposed to abiotic stress show a range of morphogenetic responses, sometimes termed the stress-induced morphogenetic response (SIMR). SIMR is principally composed of three components: inhibition of cell elongation, alterations in cell differentiation, and stimulus of cell division in localized areas. An explanation proposed for SIMR has been increased accumulation of reactive oxygen species (ROS) and alterations in hormone signaling. Mutations in the Arabidopsis thaliana RADICAL-INDUCED CELL DEATH1 (RCD1) gene have altered abiotic stress responses and ROS accumulation. Even in the absence of exogenous stress, these plants show many morphological changes also seen in SIMR. In the September issue of Plant Physiology we reported an in depth analysis of the phenotype of rcd1-3 plants as well as the phenotype of a mutations in the previously uncharacterized paralog of RCD1, SIMILAR TO RCD ONE1 (SRO1). sro1-1 plants have mild morphological changes and abiotic stress response defects while rcd1-3; sro1-1 double mutant plants have severe developmental defects, including less cell elongation. In this Addendum, we hypothesize that rcd1, sro1 and rcd1; sro1 mutant plants are under constitutive stress, and that this stress is responsible for at least some of the developmental defects seen in these plants.

Figure 1

rcd1-3; sro1-1 plants are under constitutive stress. (A) rcd1-3; sro1-1 seedlings accumulate sumoylated proteins. The upper panel shows a western blot with anti-SUM O antibody according to Xu et al. Asterisk indicates sumoylated proteins, while the lower bands are free SUM O. The lower panel shows a coomassie-stained gel showing total protein as a loading control. Lane 1, wild type; lane 2, rcd1-3; sro1-1; lane 3, nua-1; lane 4, nua-2. (B) Expression of the stress-inducible gene PARP2 is increased in rcd1-3; sro1-1 seedlings. RT -PCR done from two biological replicates with RNA extracted from seedlings is shown. Primers used to amplify PARP2 were as follows: PAR P2RT F (GCA AGC CCA CAT AA G CC G TGG AGG) and PAR P2RTR (TGC CT G CTC TT G AAT TT G TTT AC G TGC). Actin expression was used as a control; primers as in Teotia and Lamb. Lane 1, wild type; lane 2, rcd1-3; lane 3, sro1-1; lane 4, rcd1-3; sro1-1.