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ARS Home » Plains Area » Lincoln, Nebraska » Wheat, Sorghum and Forage Research » Research » Publications at this Location » Publication #323921
Title: Proteomic responses of switchgrass and prairie cordgrass to senescence

Author
item PAUDELL, BIMAL - South Dakota State University
item DAS, AAYUDH - South Dakota State University
item TRAN, MICHAELLONG - South Dakota State University
item BOE, ARVID - South Dakota State University
item Palmer, Nathan - Nate
item Sarath, Gautam
item GONZALEZ-HERNANDEZ, JOSE - South Dakota State University
item RUSHTON, PAUL - Texas A&M University
item ROHILA, JAI - South Dakota State University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2016
Publication Date: 3/14/2016
Publication URL: https://handle.nal.usda.gov/10113/62171
Citation: Paudell, B., Das, A., Tran, M., Boe, A., Palmer, N.A., Sarath, G., Gonzalez-Hernandez, J.L., Rushton, P.J., Rohila, J.S. 2016. Proteomic responses of switchgrass and prairie cordgrass to senescence. Frontiers in Plant Science. 7:293. doi: 10.3389/fpls.2016.00293.

Interpretive Summary: Switchgrass and prairie cord grass are two native warm-season grasses that have been selected as promising biofuel crops. Untimely senescence of the aerial portions of the plants can limit harvestable yields. However, plants can be selected for delayed (late) senescence which can improve biomass yields. Understanding the cellular mechanisms that promote early or late senescence could potentially yield molecular markers that can be utilized within breeding programs. One means of obtaining these cellular snapshots is using a technique termed differential proteomics. In this technique, proteins extracted from two contrasting sources are first individually tagged with a fluorescent probe that imparts a specific color to the extracted proteins. Next, equal amounts of color tagged-proteins from the two contrasting sources (early or late senescing plants) are mixed and separated by gel electrophoresis, which separates proteins according to their charge and size. Gels containing separated proteins are scanned to first detect one color and rescanned for the second color. These two color-coded images of the same gel are superimposed, and proteins enriched in one sample relative to the other will have a different color (red or green). Proteins found in common between the two extracts will have a yellow color. Following these analyses, individual spot (proteins) can be excised from the gel and subjected to analyses on a mass spectrometer. Data obtained from the mass spectrometer for individual gel pieces are compared to all the predicted proteins present in the genome of each species. These comparisons are ultimately used to identify a protein that was enriched, decreased or stayed the same in the plant extracts being compared. Using these methods leaf extracts from switchgrass and prairie cordgrass plants that differed in their timing of leaf senescence were analyzed. Data indicated that ten proteins were found in common across all plant extracts, whereas a few proteins were found to be significantly enriched in the late-senescing plants. Proteins that were specifically enriched in the late senescing plants may provide clues into the cellular mechanisms that promote delayed senescence.

Technical Abstract: Senescence in biofuel grasses is a critical issue because early senescence decreases potential biomass production by limiting aerial growth and development. 2-Dimensional,differential in-gel electrophoresis (2D-DIGE) followed by mass spectrometry of selected protein spots was used to evaluate differences between leaf proteomes of early (ES)- and late- senescing (LS) genotypes of Prairie cordgrass (ES/LS PCG) and switchgrass (ES/LS SG), just before and after senescence was initiated. Analysis of the manually filtered and statistically evaluated data indicated that 69 proteins were significantly differentially abundant across all comparisons, and a majority (41%) were associated with photosynthetic processes as determined by gene ontology analysis. Ten proteins were found in common between PCG and SG, and nine and 18 proteins were unique to PCG and SG respectively. Five of the 10 differentially abundant spots common to both species were increased in abundance, and five were decreased in abundance. Leaf proteomes of the LS genotypes of both grasses analyzed before senescence contained significantly higher abundances of a 14-3-3 like protein and a glutathione-S-transferase protein when compared to the ES genotypes, suggesting differential cellular metabolism in the LS vs. the ES genotypes. The higher abundance of 14-3-3 like proteins may be one factor that impacts the senescence process in both LS PCG and LS SG. Aconitase dehydratase was found in greater abundance in all four genotypes after the onset of senescence, consistent with literature reports from genetic and transcriptomic studies. A Rab protein of the Ras family of G proteins and an s-adenosylmethionine synthase were more abundant in ES PCG when compared with the LS PCG. In contrast, several proteins associated with photosynthesis and carbon assimilation were detected in greater abundance in LS PCG when compared to ES PCG, suggesting that a loss of these proteins potentially contributed to the ES phenotype in PCG. Overall, this study provides important data that can be utilized toward delaying senescence in both PCG and SG, and sets a foundational base for future improvement of perennial grass germplasm for greater aerial biomass productivity.