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Title: Proteome analysis of leaves of the desiccation-tolerant grass, Sporobolus stapfianus, in response to desiccation

Author
item Oliver, Melvin
item JAIN, RENUKA - University Of Missouri
item BALBUENA, TIAGO - University Of Missouri
item AGRAWAL, GANESH - University Of Missouri
item GASULLA, FRANSCISCO - Universitat De València
item THELEN, JAY - University Of Missouri

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2010
Publication Date: 11/23/2010
Citation: Oliver, M.J., Jain, R., Balbuena, T.S., Agrawal, G.K., Gasulla, F., Thelen, J.J. 2010. Proteome analysis of leaves of the desiccation-tolerant grass, Sporobolus stapfianus, in response to desiccation. Phytochemistry. 72:1273-1284.

Interpretive Summary: Drought and its effect on agricultural production is a serious issue facing global efforts to increase food supplies and ensure food security for the growing world population. Understanding how plants respond to dehydration is an important prerequisite for developing strategies for crop improvement in drought tolerance. This has proved to be a difficult task as all of the current research plant models do not tolerate cellular dehydration well and, like all crops, they succumb to the effects of relatively small water deficits. For these reasons, many researchers have started to investigate the usefulness of resurrection plants, plants that can survive extremes of dehydration to the point of desiccation, to provide answers as to how plants tolerate water loss. We have used the latest techniques in protein analysis to identify proteins whose abundance levels are altered by a dehydration event in young leaves of the resurrection grass Sporobolus stapfianus. We chose this species because of its relatively close relationship to the cereals that constitute a large portion of agriculture. Differential Gel electrophoresis and a combination of liquid chromatography and mass spectrometry were used to identify 82 differential protein isolates. From the identity of these proteins we conclude that the grass utilizes central metabolic pathways to generate carbon skeletons for the generation of protective compounds once photosynthesis ceases. We also discovered the possibility that the grass utilizes novel cell signaling compounds to regulate the establishment of dehydration tolerance. These observations give a unique “snap-shot” of the proteome of Sporobolus stapfianus at a critical point in the passage towards desiccation. Such insights and protein identifications offer new strategies for developing dehydration in our major crops, a major focus of plant breeding efforts and biotechnology.

Technical Abstract: Drought and its affects on agricultural production is a serious issue facing global efforts to increase food supplies and ensure food security for the growing world population. Understanding how plants respond to dehydration is an important prerequisite for developing strategies for crop improvement in drought tolerance. This has proved to be a difficult task as all of the current research plant models do not tolerate cellular dehydration well and, like all crops, they succumb to the effects of a relatively small water deficit of -4 MPa or less. For these reasons that many researchers have started to investigate the usefulness of resurrection plants, plants that can survive extremes of dehydration to the point of desiccation, to provide answers as to how plants tolerate water loss. We have chosen to investigate the leaf proteome response of the desiccation tolerant grass Sporobolus stapfianus Gandoger to dehydration to a water content that encompasses the initiation of the cellular protection response evident in these plants. We used a combination of two-dimensional Difference Gel Electrophoresis (2D-DIGE) and liquid chromatography-tandem-mass spectrometry to compare the proteomes of young leaves from hydrated plants to those dehydrated to approximately 30% relative water content. High resolution 2D-DIGE revealed 96 significantly different proteins and 82 of these spots were identified by mass spectrometry. Inferences from the bioinformatic annotations of these proteins revealed the possible involvement of protein kinase-based signaling cascades and brassinosteroid involvement in the regulation of the cellular protection response. Enzymes of glycolysis, both cytoplasmic and plastidic, as well as five enzymes of the Calvin cycle increased in abundance. However, the Rubisco large subunit and associated proteins were reduced, indicating a loss of carbon fixation but a continued need to supply the necessary carbon skeletons for the constituents involved in cell protection. Changes in abundance of several proteins that appear to have a function in chromatin structure and function indicate that these structures undergo significant changes as a result of dehydration. These observations give a unique “snap-shot” of the proteome of Sporobolus stapfianus at a critical point in the passage towards desiccation.