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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Sustainable Agricultural Systems Laboratory » Research » Publications at this Location » Publication #345656
Title: Physio-Genetic dissection of dark-induced leaf senescence and timing its reversal in the monocot barley

Author
item SOBIESZCZUK-NOWICKA, EWA - Adam Mickiewicz University
item WRZESINSKI, TOMASZ - Adam Mickiewicz University
item KUBALA, SZYMON - Adam Mickiewicz University
item BAGNIEWSKA-ZADWORNA, AGNIESZKA - Adam Mickiewicz University
item POLCYN, WLADYSLAW - Adam Mickiewicz University
item RUCINSKA-SOBKOWIAK, RENATA - Adam Mickiewicz University
item MISZTAL, LUCYNA - Adam Mickiewicz University
item Mattoo, Autar

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2018
Publication Date: N/A
Citation: N/A

Interpretive Summary: Senescence of leaves as seen during color change of trees in autumn is now established as a developmental and genetic program acquired during evolution. It involves energy and leads to breakdown of a plant and its organs. The question we asked is whether or not leaf senescence can be reversed. One of the established model systems for research purposes is dark-induced leaf senescence in barley. This manuscript characterizes the senescence in this model system at physiological, cytological, and genetic levels. Also, the important contribution here is the demonstration that dark-induced barley leaf senescence can be reversed within 7 days of dark incubation, and following that period, the senescence enters a new phase called programmed cell death, which is found to be irreversible. Components involved and defined markers make this study invaluable. It will be of interest to scientists, growers, and users of barley alike.

Technical Abstract: Dark-induced leaf senescence (DILS) is a good model for understanding cellular processes involved, and to test if senescence once progressed can be reversed. Physiology, transcriptome and cytology aspects of DILS were studied in the barley model. Along with cessation of photosynthesis, marked by chlorophyll fluorescence vitality index Rfd, chromatin condensation, and initiation of DNA degradation, marked by several-fold increase in the endonuclease Bnuc1, were apparent early, on day 3 of dark incubation. Disruption of nuclei shape, nucleus and mitochondria was evident only at a relatively more advanced stage of senescence and was closer to the time when programmed cell death (PCD) processes, namely, shrinking of the protoplast, tonoplast interruption and vacuole breakdown, chromatin condensation, DNA fragmentation and disintegration of the cell membrane, became aggressive. These parameters along with Rfd analysis provide early events of DILS. The decline in Rubisco protein levels occurred earlier than that of chloroplast population size and was faster than that of PsbA-encoded photosystem II reaction center D1 protein. Changes in the transcriptome were specific and five distinct gene groups were classified using hierarchical clustering, depicting GO Biological Processes. Notably, reversal of DILS by re-exposure of the plants to light was dramatic until the day 7 of dark exposure, beyond which date DILS was irreversible. Reversal of DILS on day 7 was accompanied by regaining photosynthesis, increase in chlorophyll, and reversal of Rfd. Beyond day 7 when the senescence was found irreversible, the degradation of nucleus and mitochondria - which were found stable until this point, was apparent. This later stage of DILS, the terminal phase, was also characterized by onset of autophagy.