The resurrection1 (rst1) locus of Arabidopsis controls a unique development of plant growth associated with DNA methylation and susceptibility to various pathogens

Plants continuously react to biotic and abiotic factors in the environment by altering their growth and development. Biotic stress can affect plant development and reduce the yield of agricultural crops. Plant response to pathogen attack is highly programmed and involves complex genetic regulatory network. Numerous studies have attempted to understand how plants respond to pathogen attack. In spite of this, many factors that play an important role in plant response to pathogenic fungi attack are still unknown. Our goal in this project is to enlighten our understanding of the connection between plant defense mechanisms and developmental programs associated with DNA methylation. We recently isolated a novel Arabidopsis mutant, resurrection1 (rst1), which shows reduced inflorescence stem glaucousness due to altered cuticular wax structure and composition. Three to four weeks after germination the rosette leaves of rst1 become completely necrotic, followed by the production of a new inflorescence from lateral buds (therefore the name resurrection). Interestingly, our preliminary results indicate that rst1 plants were highly susceptible to Erysiphe cichoracearum an obligate biotrophic pathogen that causes powdery mildew. However, E. cichoracearum does not germinate on the leaves of the wild type ecotype C24. Interestingly, unstable genetic segregation and variation in expression of the rst1 mutants, moreover phenotypic abnormalities of rst1 mutants lead us to suspect that Rst1 plays a role in epigenetic mechanisms. These results suggest that mutation of Rst1 has removed factors that play an important role in preventing Erysiphe cichoracearum hyphal penetration into the leaf or has derived factors that normally deter pathogen growth and invasion at the surface of leaf. From these initial data, we hypothesized that Rst1 is an important factor for pathogen interaction and plant development associated with DNA methylation. We described here the interaction between rst1 alleles and biotrophic and necrotrophic pathogens, and the abnormal growth associated with DNA hypomethylation of rst1 mutants

Induction of BAP1 by a Moderate Decrease in Temperature Is Mediated by ICE1 in Arabidopsis1[C][OA]

Temperature variations at the nonextreme range modulate various processes of plant growth, development, and physiology, but how plants perceive and transduce these temperature signals is not well understood. Moderate cooling from 28°C to 22°C induces transcription of a number of genes in salicylic acid-dependent and -independent manners. Here, we report the study of the transcriptional control of the BON1-ASSOCIATED PROTEIN1 (BAP1) gene that is responsive to a moderate decrease of temperature as well as to many environmental stimuli. Using reporter genes under the control of series of regions of the BAP1 promoter, we identified a 35-bp fragment that is necessary and sufficient for the BAP1 transcript induction by a moderate cooling. This fragment also confers an induction of BAP1 by cold and reactive oxygen species-generating paraquat. Furthermore, the INDUCER OF CBF EXPRESSION1 (ICE1) protein that is involved in transcriptional control of cold responses is found to bind to a MYC element in this promoter and is required for the cooling induction of BAP1. The ice1 mutant has a low induction of BAP1 and enhanced resistance to a bacterial pathogen. Thus, responses to a moderate decrease in temperature may utilize components in the cold response as well as a potentiating signaling involving salicylic acid

The Arabidopsis RESURRECTION1 Gene Regulates a Novel Antagonistic Interaction in Plant Defense to Biotrophs and Necrotrophs1[W][OA]

We report a role for the Arabidopsis (Arabidopsis thaliana) RESURRECTION1 (RST1) gene in plant defense. The rst1 mutant exhibits enhanced susceptibility to the biotrophic fungal pathogen Erysiphe cichoracearum but enhanced resistance to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola. RST1 encodes a novel protein that localizes to the plasma membrane and is predicted to contain 11 transmembrane domains. Disease responses in rst1 correlate with higher levels of jasmonic acid (JA) and increased basal and B. cinerea-induced expression of the plant defensin PDF1.2 gene but reduced E. cichoracearum-inducible salicylic acid levels and expression of pathogenesis-related genes PR1 and PR2. These results are consistent with rst1's varied resistance and susceptibility to pathogens of different life styles. Cuticular lipids, both cutin monomers and cuticular waxes, on rst1 leaves were significantly elevated, indicating a role for RST1 in the suppression of leaf cuticle lipid synthesis. The rst1 cuticle exhibits normal permeability, however, indicating that the disease responses of rst1 are not due to changes in this cuticle property. Double mutant analysis revealed that the coi1 mutation (causing defective JA signaling) is completely epistatic to rst1, whereas the ein2 mutation (causing defective ethylene signaling) is partially epistatic to rst1, for resistance to B. cinerea. The rst1 mutation thus defines a unique combination of disease responses to biotrophic and necrotrophic fungi in that it antagonizes salicylic acid-dependent defense and enhances JA-mediated defense through a mechanism that also controls cuticle synthesis