Ke Mao1, Jie Yang1, Min Wang1, Huayu Liu1, Xin Guo1, Shuang Zhao1, Qinglong Dong1, Fengwang Ma2. 1. State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A &F University, Yangling, 712100, Shaanxi, China. 2. State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A &F University, Yangling, 712100, Shaanxi, China. fwm64@nwsuaf.edu.cn.
Abstract
BACKGROUND: Calcium (Ca2+) plays an important role in plant growth and development, and the maintenance of calcium homeostasis is necessary for the survival of all plant species. Ca2+/H+ exchangers (CAXs) are a subgroup of the CaCA (Ca2+/cation antiporter) superfamily. In general, CAX proteins mediate cytosolic Ca2+ entry into vacuoles to prevent excessive accumulation of Ca2+ in the cytosol. The CaCA superfamily has been identified and characterised in many plant species; however, characterisation of the CaCA superfamily and functional study of apple CAX proteins have yet to be conducted in apple (Malus × domestica Borkh.). RESULTS: Here, we identified 21 CaCA family proteins in apple for the first time. Phylogenetic and gene structure analysis, as well as prediction of conserved motifs, suggested that these proteins could be classified into four groups: CAX, CCX, NCL, and MHX. Expression analysis showed that the 10 MdCAX genes we cloned strongly responded to calcium and abiotic stress treatments. Collinearity analysis and characterisation of calcium transport capacity resulted in the identification of a pair of segmental duplication genes: MdCAX3L-1 and MdCAX3L-2; MdCAX3L-2 showed strong calcium transport capacity, whereas MdCAX3L-1 showed no calcium transport capacity. Yeast two-hybrid (Y2H) assays showed that these two proteins could interact with each other. The high sequence similarity (94.6%) makes them a good model for studying the crucial residues and structural basis of the calcium transport of CAX proteins. Prediction of the protein interaction network revealed several proteins that may interact with CAX proteins and play important roles in plant stress responses, such as SOS2, CXIP1, MHX, NRAMP3, and MTP8. CONCLUSIONS: Our analysis indicated that MdCAX proteins have strong calcium transport capacity and are involved in the abiotic stress response in apple. These findings provide new insight and rich resources for future studies of MdCAX proteins in apple.
BACKGROUND:Calcium (Ca2+) plays an important role in plant growth and development, and the maintenance of calcium homeostasis is necessary for the survival of all plant species. Ca2+/H+ exchangers (CAXs) are a subgroup of the CaCA (Ca2+/cation antiporter) superfamily. In general, CAX proteins mediate cytosolic Ca2+ entry into vacuoles to prevent excessive accumulation of Ca2+ in the cytosol. The CaCA superfamily has been identified and characterised in many plant species; however, characterisation of the CaCA superfamily and functional study of apple CAX proteins have yet to be conducted in apple (Malus × domestica Borkh.). RESULTS: Here, we identified 21 CaCA family proteins in apple for the first time. Phylogenetic and gene structure analysis, as well as prediction of conserved motifs, suggested that these proteins could be classified into four groups: CAX, CCX, NCL, and MHX. Expression analysis showed that the 10 MdCAX genes we cloned strongly responded to calcium and abiotic stress treatments. Collinearity analysis and characterisation of calcium transport capacity resulted in the identification of a pair of segmental duplication genes: MdCAX3L-1 and MdCAX3L-2; MdCAX3L-2 showed strong calcium transport capacity, whereas MdCAX3L-1 showed no calcium transport capacity. Yeast two-hybrid (Y2H) assays showed that these two proteins could interact with each other. The high sequence similarity (94.6%) makes them a good model for studying the crucial residues and structural basis of the calcium transport of CAX proteins. Prediction of the protein interaction network revealed several proteins that may interact with CAX proteins and play important roles in plant stress responses, such as SOS2, CXIP1, MHX, NRAMP3, and MTP8. CONCLUSIONS: Our analysis indicated that MdCAX proteins have strong calcium transport capacity and are involved in the abiotic stress response in apple. These findings provide new insight and rich resources for future studies of MdCAX proteins in apple.
Authors: Riccardo Velasco; Andrey Zharkikh; Jason Affourtit; Amit Dhingra; Alessandro Cestaro; Ananth Kalyanaraman; Paolo Fontana; Satish K Bhatnagar; Michela Troggio; Dmitry Pruss; Silvio Salvi; Massimo Pindo; Paolo Baldi; Sara Castelletti; Marina Cavaiuolo; Giuseppina Coppola; Fabrizio Costa; Valentina Cova; Antonio Dal Ri; Vadim Goremykin; Matteo Komjanc; Sara Longhi; Pierluigi Magnago; Giulia Malacarne; Mickael Malnoy; Diego Micheletti; Marco Moretto; Michele Perazzolli; Azeddine Si-Ammour; Silvia Vezzulli; Elena Zini; Glenn Eldredge; Lisa M Fitzgerald; Natalia Gutin; Jerry Lanchbury; Teresita Macalma; Jeff T Mitchell; Julia Reid; Bryan Wardell; Chinnappa Kodira; Zhoutao Chen; Brian Desany; Faheem Niazi; Melinda Palmer; Tyson Koepke; Derick Jiwan; Scott Schaeffer; Vandhana Krishnan; Changjun Wu; Vu T Chu; Stephen T King; Jessica Vick; Quanzhou Tao; Amy Mraz; Aimee Stormo; Keith Stormo; Robert Bogden; Davide Ederle; Alessandra Stella; Alberto Vecchietti; Martin M Kater; Simona Masiero; Pauline Lasserre; Yves Lespinasse; Andrew C Allan; Vincent Bus; David Chagné; Ross N Crowhurst; Andrew P Gleave; Enrico Lavezzo; Jeffrey A Fawcett; Sebastian Proost; Pierre Rouzé; Lieven Sterck; Stefano Toppo; Barbara Lazzari; Roger P Hellens; Charles-Eric Durel; Alexander Gutin; Roger E Bumgarner; Susan E Gardiner; Mark Skolnick; Michael Egholm; Yves Van de Peer; Francesco Salamini; Roberto Viola Journal: Nat Genet Date: 2010-08-29 Impact factor: 38.330