Abiotic Stress/Whole Plant Bio

Abstract

CS-4-6 - Involvement of NPR1 in chloroplast-mediated retrograde signaling to the nucleus in response to salt stress.

Sunday, July 15
2:43 PM - 2:45 PM

A fundamental question of plant physiology and cell biology is: how do organelles communicate with the nucleus to coordinate genetic programs and cellular functions? Although several potential retrograde signals originating from chloroplasts for physiological processes in response to abiotic and biotic stresses are known to modulate nuclear gene expression, the movement of such signaling components and their structural pathways remain largely uncharacterized. Here, we found that nonexpressor of pathogenesis-related genes 1 (NPR1) protein, a transcriptional coactivator, transiently accumulated in chloroplasts under salt stress, followed by its sequestration from chloroplasts to the nucleus accompanied by post-translational modifications. NPR1-GFP monomers with a 93 KDa and oligomers with sizes of at least than 200 to 400 kDa (dimer to tetramer) as well as a smaller molecule with a 45 kDa were detected in the stroma proteins of salt-stressed p35S::Trp-NPR1-GFP transgenic plants. However, only 45 kDa molecule of NPR1-GFP was detected in nuclear proteins from this transgenic line. Reactive oxygen species (ROS) are key regulators of redox homeostasis in living organisms. Chloroplast-mediated translocation of NPR1 was enhanced by stress-induced ROS and ethylene production, which are synergistically enhanced in a biphasic manner during stresses. NPR1 movement was disrupted by lincomycin, an inhibitor of protein synthesis in chloroplasts, suggesting some chloroplast components were required for this retrograde signaling. Involvement of stromules or stromule-related endoplasmic reticulum is detected in NPR1 movements. Furthermore, regarding gene expression of stress-responsible proteins and retrograde signaling candidates, NPR1-dependent changes in chloroplast-encoded chloroplast protein levels were followed by alteration of nuclear-encoded chloroplast protein levels. Taken together, NPR1 is a retrograde signaling protein that regulates genetic reprogramming after being modified in chloroplasts and might serve as a sensitive controller of environmental messages to the nucleus. Sress-induced chloroplast ROS affects gene expression by the sequestration of redox-sensitive transcription factors or transcription coactivators.


 

Co-Authors

So Yeon Seo – Sunchon National University; Soo Jin Wi – Sunchon National University

Ky Young Park

Professor
Sunchon National University

Presentation(s):

Send Email for Ky Young Park


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CS-4-6 - Involvement of NPR1 in chloroplast-mediated retrograde signaling to the nucleus in response to salt stress.



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