Inter-organellar communication during innate immunity
S. DINESH-KUMAR (1), E. Park (1), A. Kumar (2), A. Alqarni (2), A. Nedo (2), L. Ren (2), K. Hoban (2), M. Padmanabhan (1), S. Modla (2), C. Kambhamettu (2), J. Caplan (2) (1) University of California, Davis, U.S.A.; (2) University of Delaware, U.S.A.

Emerging evidence suggests that chloroplasts play an important function during innate immunity and they also have a central role in the production of immune signals including reactive oxygen species (ROS), calcium (Ca2+) transients, and defense hormones, such as salicylic acid (SA) and jasmonic acid (JA). Our recent findings demonstrated that chloroplasts dynamically change their morphology by sending out stroma-filled tubular projections known as stromules during immune responses. Interestingly, stromules form complex associations with the nuclei and subsequent clustering of chloroplasts around nuclei during immune response. The increase in surface area of chloroplast tubule extensions could aid in the transfer of pro-defense signals and/or other signaling proteins or metabolites from chloroplasts to the cytosol and nucleus to activate defense signaling. Our findings show that hydrogen peroxide (H2O2) and SA can induce stromules and H2O2 can move through these chloroplast-to-nuclear connections. Furthermore, a chloroplast-localized defense protein NRIP1 accumulates in the nucleus during an immune response possibly via chloroplast-to-nuclear associations. Consistent with these findings, constitutive induction of stromules leads to enhanced programmed cell death (PCD) response. We will discuss our recent results on stromule function, chloroplast association with nuclei, and the role of cytoskeleton during PCD and plant innate immunity.

Abstract Number: P4-2
Session Type: Plenary