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Potomac Division - Xanthomonas effector AvrRxo1 suppresses plant immunity by regulating the plant stomatal aperture sizes
S. WU (1), C. Zhou (1), Y. Liu (1), Q. Cheng (2), B. Zhao (1). (1) Virginia Tech, Blacksburg, VA, U.S.A.; (2) Nanjing Forestry University, Nanjing, China

Rice bacterial leaf streak disease caused by <i>Xanthomonas</i> <i>oryzae</i> pv. <i>oryzicola</i> (<i>Xoc</i>) is one of the most important bacterial diseases in rice fields. A type III effector gene <i>avrRxo1</i> was isolated from the genome of <i>Xoc</i>. Ectopic expression of <i>avrRxo1</i> in Arabidopsis could suppress plant immunity in Arabidopsis. In aim to identify the virulent targets of AvrRxo1, we screened two Arabidopsis yeast two-hybrid cDNA libraries by using AvrRox1 as the bait. As a result, AIN2 was identified as a putative transcription factor that has two homologues in the <i>Arabidopsis</i> genome. And AvrRxo1’s virulence function was compromised on the mutant of <i>ain2</i>. To identify Arabidopsis genes regulated by AvrRxo1 and AIN2, we performed RNA-seq analysis on the <i>AvrRxo1</i> transgenic and <i>ain2</i> mutant Arabidopsis plant, which allows us to identify a collection of AvrRxo1 induced genes (AIG). We further demonstrated that AvrRxo1 stabilized Ain2, in order to induce the expression of its direct target gene <i>aig1</i>. Overexpression of <i>aig1</i> in Arabidopsis inhibited stomata closing, and suppressed plant immunity. Our result illustrated AvrRxo1 manipulated Ain2 to compromise Arabidopsis defense system, which suggested Ain2 plays an important role in plant immunity. Further characterization of Ain2 in Arabidopsis may help us gain new insight of plant immunity and develop new strategy to achieve durable disease resistance in crop plants.

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