Poster abstracts

Poster number 57 submitted by Sachin Teotia

Two putative poly (ADP-ribose) polymerases, RCD1 and SRO1, play important, partially redundant roles in Arabidopsis development

Sachin Teotia (MCDB, The Ohio State University), Rebecca S. Lamb (PCMB and MCDB, The Ohio State University)

Abstract:
RADICAL-INDUCED CELL DEATH1 (RCD1) and SIMILAR TO RCD ONE1 (SRO1) are the only two proteins encoded in the Arabidopsis genome containing both a putative poly (ADP-ribose) polymerase (PARP) catalytic domain and a WWE protein-protein interaction domain. Proteins with a similar domain structure have been found in other eukaryotes. PARPs mediate attachment of ADP-ribose units from donor NAD+ molecules to target proteins and have been implicated in a number of processes including DNA repair, apoptosis, transcription, and chromatin remodeling. Like RCD1, SRO1 is expressed in all plant organs. We have isolated mutants in both RCD1 and SRO1, rcd1-3 and sro1-1, respectively. rcd1-3 plants display similar phenotypic defects to those reported for previously isolated alleles, most notably reduced stature. In addition, rcd1-3 mutants display abnormal phyllotaxy, abnormal floral organs, increased lateral root number and length, and shorter primary roots. sro1-1 plants display some subtle developmental defects in the roots but otherwise develop normally. The lack of visible phenotypes in sro1-1 mutants could be due to redundancy with RCD1. However, rcd1-3 plants are early flowering under both long and short days, in contrast sro1-1 plants flower late. This suggests that the genes do not always function equivalently. Loss of a single dose of SRO1 in the rcd1-3 background increases the severity of dwarfing, suggesting these two genes may share some functions. Consistent with this, rcd1-3; sro1-1 double mutants display severe developmental problems like embryo and seed abnormalities, reduced germination, extreme dwarfism, abnormal flowers, and short siliques. The basis for these defects and the exact nature of the redundancy between these two paralogous genes is currently being examined.

References:
1. Ahlfors, R. et al., (2004). Arabidopsis RADICAL-INDUCED CELL DEATH1 belongs to the WWE protein-protein interaction domain protein family and modulates abscisic acid, ethylene, and methyl jasmonate responses.
2. Aravind, L. (2001). The WWE domain: a common interaction module in protein ubiquitination and ADP ribosylation.
3. Belles-Boix, et al., (2000). rcd1-3, a new protein from Arabidopsis thaliana, protects yeast against oxidative damage.
4. Fujibe, T. et al., (2004). A methyl viologen-resistant mutant of Arabidopsis, which is allelic to ozone-sensitive rcd1, is tolerant to supplemental ultraviolet-B irradiation.
5. Katiyar-Agarwal S. et al., (2006)The plasma membrane Na+/H+ antiporter SOS1 interacts with RCD1 and functions in oxidative stress tolerance in Arabidopsis.

Keywords: RCD1 and SRO1, PARP, Arabidopsis