title: Quantitative proteomic analysis of two different rice varieties reveals that drought tolerance is correlated with reduced abundance of photosynthetic machinery and increased abundance of ClpD1 protease.
abstract: Rice is the major staple food for more than half of world's population. As global climate changes, we are observing more floods, droughts and severe heat waves. Two rice cultivars with contrasting genetic backgrounds and levels of tolerance to drought, Nipponbare and IAC1131, were used in this study. Four-week-old seedlings of both cultivars were grown in large soil volumes and then exposed to moderate and extreme drought for 7days, followed by 3days of re-watering. Mature leaves were harvested from plants from each treatment for protein extraction and subsequent shotgun proteomic analysis, with validation of selected proteins by western blotting. Gene Ontology (GO) annotations of differentially expressed proteins provide insights into the metabolic pathways that are involved in drought stress resistance. Our data indicate that IAC1131 appears to be better able to cope with stressful conditions by upregulating a suite of stress and defence response related proteins. Nipponbare, in contrast, lacks the range of stress responses shown by the more stress tolerant variety, and responds to drought stress by initiating a partial shutdown of chlorophyll biosynthesis in an apparent attempt to preserve resources.
  
  
  
  In this study, two rice genotypes with contrasting drought tolerance were exposed to soil water deficits, and proteomic changes were observed in mature leaf laminae. Plants were well watered and then switched to conditions of either moderate drought or extreme drought followed by three days of recovery. Proteins were identified and quantified using both label-free and Tandem Mass Tag multiplexing approaches. Several biochemical pathways were significantly altered in response to water deficit. Most notably, the up-regulation of ClpD1 protease responded strongly in the drought-tolerant landrace; this protein is typically involved in heat and osmotic stress response. In contrast, porphyrin and chlorophyll biosynthesis pathways were down-regulated, indicating suppression of the photosynthetic machinery.
authors.affiliation: Department of Chemistry and Biomolecular Sciences, Macquarie University, North Ryde, NSW, Australia.
authors.forename: Yunqi
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Chemistry and Biomolecular Sciences, Macquarie University, North Ryde, NSW, Australia.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Mirzaei
authors.affiliation: Australian Proteome Analysis Facility, Macquarie University, North Ryde, NSW, Australia.
authors.forename: Dana
authors.initials: D
authors.lastname: Pascovici
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Joel M
authors.initials: JM
authors.lastname: Chick
authors.affiliation: Department of Biological Sciences, Macquarie University, North Ryde, NSW, Australia.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Atwell
authors.affiliation: Department of Chemistry and Biomolecular Sciences, Macquarie University, North Ryde, NSW, Australia. Electronic address: paul.haynes@mq.edu.au.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Haynes
mesh_terms: D000222:Adaptation, Physiological; D002734:Chlorophyll / Q000096:biosynthesis; D055864:Droughts; D049071:Endopeptidase Clp / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D053858:Metabolic Networks and Pathways; D012275:Oryza / Q000737:chemistry / Q000201:enzymology*; D010788:Photosynthesis / Q000235:genetics; D018515:Plant Leaves / Q000737:chemistry; D010940:Plant Proteins / Q000302:isolation & purification; D040901:Proteomics / Q000379:methods*; D013045:Species Specificity; D013312:Stress, Physiological
chemical_list: D010940:Plant Proteins; D002734:Chlorophyll; D049071:Endopeptidase Clp
keywords: Abiotic stress; ClpD1 protease; Drought tolerance; Plant proteomics; Rice; Shotgun proteomics