title: Genome-wide identification of rubber tree (Hevea brasiliensis Muell. Arg.) aquaporin genes and their response to ethephon stimulation in the laticifer, a rubber-producing tissue.
abstract: BACKGROUND
  Natural rubber, an important industrial raw material, is specifically synthesized in laticifers located inside the rubber tree (Hevea brasiliensis Muell. Arg.) trunk. Due to the absence of plasmodesmata, the laticifer water balance is mediated by aquaporins (AQPs). However, to date, the characterization of H. brasiliensis AQPs (HbAQPs) is still in its infancy.
  
  
  RESULTS
  In this study, 51 full-length AQP genes were identified from the rubber tree genome. The phylogenetic analysis assigned these AQPs to five subfamilies, including 15 plasma membrane intrinsic proteins (PIPs), 17 tonoplast intrinsic proteins (TIPs), 9 NOD26-like intrinsic proteins (NIPs), 4 small basic intrinsic proteins (SIPs) and 6 X intrinsic proteins (XIPs). Functional prediction based on the analysis of the aromatic/arginine (ar/R) selectivity filter, Froger's positions and specificity-determining positions (SDPs) showed a remarkable difference in substrate specificity among subfamilies. Homology analysis supported the expression of 44 HbAQP genes in at least one of the examined tissues. Furthermore, deep sequencing of the laticifer transcriptome in the form of latex revealed a key role of several PIP subfamily members in the laticifer water balance, and qRT-PCR analysis showed diverse expression patterns of laticifer-expressed HbAQP genes upon ethephon treatment, a widely-used practice for the stimulation of latex yield.
  
  
  CONCLUSIONS
  This study provides an important genetic resource of HbAQP genes, which will be useful to improve the water use efficiency and latex yield of Hevea.
authors.affiliation: Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, 571737, P. R. China. zouzhi2008@126.com.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Zou
authors.affiliation: Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, 571737, P. R. China. 378201617@qq.com.
authors.forename: Jun
authors.initials: J
authors.lastname: Gong
authors.affiliation: Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, 571737, P. R. China. an-f@163.com.
authors.forename: Feng
authors.initials: F
authors.lastname: An
authors.affiliation: Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, 571737, P. R. China. xie23300459@163.com.
authors.forename: Guishui
authors.initials: G
authors.lastname: Xie
authors.affiliation: Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, 571737, P. R. China. kunjiwang@163.com.
authors.forename: Jikun
authors.initials: J
authors.lastname: Wang
authors.affiliation: Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, 571737, P. R. China. 23306788@163.com.
authors.forename: Yeyong
authors.initials: Y
authors.lastname: Mo
authors.affiliation: Danzhou Investigation & Experiment Station of Tropical Crops, Ministry of Agriculture, Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou, 571737, P. R. China. ylfri@126.com.
authors.forename: Lifu
authors.initials: L
authors.lastname: Yang
mesh_terms: D020346:Aquaporins / Q000737:chemistry / Q000235:genetics*; D005091:Exons; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D023061:Gene Order; D055106:Genome-Wide Association Study; D028482:Hevea / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D007438:Introns; D005810:Multigene Family; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D012408:Rubber / Q000378:metabolism; D059467:Transcriptome
chemical_list: D020346:Aquaporins; D009943:Organophosphorus Compounds; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012408:Rubber; C005073:ethephon