up over generations to respond to dynamic environments, such as increased predation and extreme temperatures.A. thaliana has also been used to study SAR. This pathway uses benzothiadiazol, a chemical inducer, to induce transcription factors, mRNA, of SAR genes. This accumulation of transcription factors leads to inhibition of pathogen-related genes. Plant-pathogen interactions are important for an understanding of how plants have evolved to combat different types of pathogens that may affect them. Variation in resistance of plants across populations is due to variation in environmental factors. Plants that have evolved resistance, whether it be the general variation or the SAR variation, have been able to live longer and hold off necrosis of their tissue (premature death of cells), which leads to better adaptation and fitness for populations that are in rapidly changing environments. In the future, comparisons of the pathosystems of wild populations + their coevolved pathogens with wild-wild hybrids of known parentage may reveal new mechanisms of balancing selection. In life history theory we may find that A. thaliana maintains certain alleles due to pleitropy between plant-pathogen effects and other traits, as in livestock. Research in A. thaliana suggests that the immunity regulator protein family EDS1 in general co-evolved with the CC family of nucleotide-bindingleucine-rich-repeat-receptors (NLRs). Xiao et al. 2005 have shown that the powdery mildew immunity mediated by A. thalianas RPW8 (which has a CC domain) is dependent on two members of this family: EDS1 itself and PAD4.RESISTANCE TO PSEUDOMONAS SYRINGAE 5/RPS5 is a disease resistance protein which guards AvrPphB SUSCEPTIBLE 1/PBS1. PBS1, as the name would suggest, is the target of AvrPphB, an effector produced by Pseudomonas syringae pv. phaseolicola. Other research Ongoing research on A. thaliana is being performed on the International Space Station by the European Space Agency. The goals are to study the growth and reproduction of plants from seed to seed in microgravity. Plant-on-a-chip devices in which A. thaliana tissues can be cultured in semi-in vitro conditions have been described. Use of these devices may aid understanding of pollen-tube guidance and the mechanism of sexual reproduction in A. thaliana.Researchers at the University of Florida were able to grow the plant in lunar soil originating from the Sea of Tranquillity. Self-pollinationA. thaliana is a predominantly self-pollinating plant with an outcrossing rate estimated at less than 0.3%. An analysis of the genome-wide pattern of linkage disequilibrium suggested that self-pollination evolved roughly a million years ago or