title: Molecular characterization and expression analysis of the small GTPase ROP members expressed in laticifers of the rubber tree (Hevea brasiliensis).
abstract: ROP (Rho of plants) proteins are plant-specific Rho-type small GTPases which play important roles in cellular processes and stress responses. This study explores the characteristics and possible functions of ROPs that are expressed primarily in laticifers of the rubber tree (Hevea brasiliensis). The work serves as a preliminary step to determining their involvement in latex flow and regeneration, laticifers formation and tapping panel dryness (TPD, a physiological disorder in rubber trees that result in the stoppage of latex flow). In this connection, we (i) identified five HbROPs (HbROP1-HbROP5) by searching latex transcripts database and the genome databases, (ii) characterized molecular and phylogenic aspects of the HbROPs and examined the cis-regulatory elements in their promoter regions; (iii) analyzed by Real-time Quantitative PCR (QPCR) the tissue specificity of the HbROPs and their expression patterns in response to tapping, bark wounding and growth regulator treatments. All five HbROP genes were strongly expressed in the latex, with HbROP1, 3, 4 and 5 showing the highest expression among the six Hevea tissues examined, viz. latex, bud, mature leaf, bark, male flower and seed. When tapping was initiated on previously untapped trees, HbROP3 transcription was substantially down-regulated whereas HbROP5 expression was markedly up-regulated. Transcripts of HbROP3 rose gradually with the development of TPD. Except for the cytokinin 6-benzyl aminopurine that induced a rise in HbROP5 transcripts by more than 2-fold, the other growth regulators tested had little effect on HbROPs expression. The roles of HbROPs in rubber tree are discussed in relation to the diverse functions of ROP homologs reported in other plant species.
authors.affiliation: Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Danzhou, Hainan 571737, China.
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Danzhou, Hainan 571737, China; College of Agronomy, Hainan University, Haikou, Hainan 570228, China.
authors.forename: Yacheng
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Danzhou, Hainan 571737, China.
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Fang
authors.affiliation: Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Danzhou, Hainan 571737, China.
authors.forename: Jiyan
authors.initials: J
authors.lastname: Qi
authors.affiliation: Rubber Research Institute, Chinese Academy of Tropical Agricultural Sciences, Key Laboratory of Biology and Genetic Resources of Rubber Tree, Ministry of Agriculture, Danzhou, Hainan 571737, China. Electronic address: chaorongtang@126.com.
authors.forename: Chaorong
authors.initials: C
authors.lastname: Tang
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D003583:Cytokinins / Q000502:physiology; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D028482:Hevea / Q000201:enzymology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D003583:Cytokinins; D017931:DNA Primers; D018076:DNA, Complementary; D020558:GTP Phosphohydrolases
keywords: Gene cloning and expression; Hevea brasiliensis; Latex regeneration; Phylogenic analysis; ROP; Tapping panel dryness