Insights into rubber biosynthesis from transcriptome analysis of Hevea brasiliensis latex.
Hevea brasiliensis is the most widely cultivated species for commercial production of natural rubber (cis-polyisoprene). In this study, 10,040 expressed sequence tags (ESTs) were generated from the latex of the rubber tree, which represents the cytoplasmic content of a single cell type, in order to analyse the latex transcription profile with emphasis on rubber biosynthesis-related genes. A total of 3,441 unique transcripts (UTs) were obtained after quality editing and assembly of EST sequences. Functional classification of UTs according to the Gene Ontology convention showed that 73.8% were related to genes of unknown function. Among highly expressed ESTs, a significant proportion encoded proteins related to rubber biosynthesis and stress or defence responses. Sequences encoding rubber particle membrane proteins (RPMPs) belonging to three protein families accounted for 12% of the ESTs. Characterization of these ESTs revealed nine RPMP variants (7.9-27 kDa) including the 14 kDa REF (rubber elongation factor) and 22 kDa SRPP (small rubber particle protein). The expression of multiple RPMP isoforms in latex was shown using antibodies against REF and SRPP. Both EST and quantitative reverse transcription-PCR (QRT-PCR) analyses demonstrated REF and SRPP to be the most abundant transcripts in latex. Besides rubber biosynthesis, comparative sequence analysis showed that the RPMPs are highly similar to sequences in the plant kingdom having stress-related functions. Implications of the RPMP function in cis-polyisoprene biosynthesis in the context of transcript abundance and differential gene expression are discussed.
Chow
Keng-See
KS
Biotechnology Unit, Rubber Research Institute of Malaysia, Malaysian Rubber Board, RRIM Experiment Station, 47000 Sungai Buloh, Selangor, Malaysia. kschow@lgm.gov.my
Wan
Kiew-Lian
KL
Isa
Mohd Noor Mat
MN
Bahari
Azlina
A
Tan
Siang-Hee
SH
Harikrishna
K
K
Yeang
Hoong-Yeet
HY
D000595:Amino Acid Sequence; D019295:Computational Biology; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D028482:Hevea / Q000235:genetics* / Q000378:metabolism; D007840:Latex / Q000096:biosynthesis*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D012408:Rubber / Q000378:metabolism*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D014158:Transcription, Genetic
D007840:Latex; D008565:Membrane Proteins; D010940:Plant Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D012408:Rubber