title: Physiological and proteome analysis suggest critical roles for the photosynthetic system for high water-use efficiency under drought stress in Malus.
abstract: Water use efficiency is an important indicator for plant adaptation and resistance to drought conditions. We previously found that under moderate drought stress, the water use efficiency of cv. 'Qinguan' apple (Malus domestica Borkh.) (tolerant to drought) was enhanced, while that of cv. 'Naganofuji No. 2' was not enhanced. In this research, we also found that instantaneous water-use efficiency of cv. 'Qinguan' was higher than that of cv. 'Naganofuji No. 2', mainly because of its higher net photosynthesis rate. To dissect the potential mechanisms underlying this phenomenon, we performed a comparative iTRAQ-based proteomics analysis with leaves of drought-treated cv. 'Qinguan' and 'Naganofuji No. 2'. We identified 4078 proteins, of which 594 were differentially abundant between drought and well-watered leaves. The majority of increased proteins were predicted to be involved in photosynthetic pathway in drought treated cv. 'Qinguan' leaves, indicating that regulation of photosynthesis plays an important role for higher water use efficiency under drought stress. Enzyme activity assays were performed to validate the proteomics data. Our results suggested that the main regulatory mechanisms for high water use efficiency of cv. 'Qinguan' under moderate drought stress included the maintaining of Calvin cycle function by increasing key enzymes, stabilization of photosynthetic electron transfer and keeping reactive oxygen species at normal level by regulation of photosynthetic electron transfer chain, photorespiration and reactive oxygen species scavenging capability, thus prevented photoinhibition, reduced reactive oxygen species production and enhanced net photosynthesis rate. In addition, the response of signal regulatory proteins and abiotic stress-responsive proteins to drought also helped plants to cope with such stress.
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: zhoushasha198609@126.com.
authors.forename: Shasha
authors.initials: S
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: limingjun@nwsuaf.edu.cn.
authors.forename: Mingjun
authors.initials: M
authors.lastname: Li
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: qguan@nwsuaf.edu.cn.
authors.forename: Qingmei
authors.initials: Q
authors.lastname: Guan
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: 782283217@qq.com.
authors.forename: Fengli
authors.initials: F
authors.lastname: Liu
authors.affiliation: Institute of Biotechnology, Cornell University, Ithaca, NY 14853, USA. Electronic address: sz14@cornell.edu.
authors.forename: Sheng
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Institute of Biotechnology, Cornell University, Ithaca, NY 14853, USA. Electronic address: wc456@cornell.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: yinlhua@163.com.
authors.forename: Lihua
authors.initials: L
authors.lastname: Yin
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: gougouqy@163.com.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Qin
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: fwm64@nwsuaf.edu.cn.
authors.forename: Fengwang
authors.initials: F
authors.lastname: Ma
mesh_terms: D000222:Adaptation, Physiological; D055864:Droughts; D027845:Malus / Q000235:genetics / Q000502:physiology*; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D020543:Proteome / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological; D014867:Water / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D020543:Proteome; D014867:Water
keywords: Apple; Moderate drought; Water use efficiency; iTRAQ-based proteomics