Study of expression changes during RPS4-mediated resistance in Arabidopsis using a temperature-inducible system

Innate immune responses of plant cells confer the first line of defence against pathogens. Signals generated by activated receptors are integrated inside the cell and converge on transcriptional programmes in the nucleus. The Arabidopsis Toll-related intracellular receptor RPS4 operates inside nuclei to trigger resistance to Pseudomonas bacteria expressing AvrRps4 and defence gene reprogramming through the stress response regulator, EDS1. In this immune response, RPS4 cooperates genetically with RRS1 encoding a nuclear TIR-NB-LRR receptor with an additional C-terminal ‘WRKY’ DNA-binding domain. Using transgenic Arabidopsis plants constitutively expressing RPS4 (35S:RPS4), an EDS1-dependent immune response can be turned on rapidly and synchronously in leaf cells after a switch from high (28°C) to moderate (19°C) temperature. In order to determine the relative contributions of RRS1 and EDS1 to temperature-conditioned 35S:RPS4-HS transcriptional reprogramming, we performed gene expression microarray analysis of 35S:RPS4-HS, 35S:RPS4-HS rrs1-11 and 35S:RPS4-HS eds1-2 leaf mRNAs before and after temperature shift. We used transgenic Arabidopsis plants over-expressing RPS4 in EDS1 WT, eds1-2 or rrs1-11 mutant backgrounds. 35S:RPS4, 35S:RPS4 eds1-2 and 35S:RPS4 rrs1-11 plants were grown at 28°C for 3.5 weeks, and subsequently shifted to 19°C. Samples were collected before shift (0h) and 2, 8 and 24h after shift, in triplicates.