RESUMO
Tapping panel dryness (TPD) is a complex physiological syndrome found widely in rubber tree (Hevea brasiliensis) plantations that causes severe yield loss in natural rubber-producing countries. In an earlier study, we confirmed that there is a negative correlation between HbMyb1 expression and TPD severity. To further investigate the function of HbMyb1 in TPD, HbMyb1 was over-expressed in tobacco controlled by a CaMV 35S promoter. In transgenic plants expressing HbMyb1, cell death induced by UV-B irradiation, paraquat and the hypersensitive reaction to necrotrophic fungal infection (Botrytis cinerea) was suppressed with a close correlation between HbMyb1 protein levels and the extent of suppression. In addition the nuclear condensation and degradation were observed in laticifer cells of TPD trees, while the nucleus of laticifer cells of healthy trees was morphologically normal. On the basis of the results described above, we propose that HbMyb1 maybe suppress stress induced cell death in rubber trees.
Assuntos
Adaptação Fisiológica/genética , Morte Celular/genética , Hevea/fisiologia , Nicotiana/fisiologia , Doenças das Plantas/genética , Estresse Fisiológico/genética , Fatores de Transcrição/metabolismo , Botrytis , Núcleo Celular , Expressão Gênica , Genes de Plantas , Hevea/genética , Hevea/metabolismo , Paraquat , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Valores de Referência , Nicotiana/genética , Nicotiana/metabolismo , Fatores de Transcrição/genética , Árvores , Raios UltravioletaRESUMO
BACKGROUND: Tapping panel dryness (TPD) is one of the most serious threats to natural rubber production. Although a great deal of effort has been made to study TPD in rubber tree, the molecular mechanisms underlying TPD remain poorly understood. Identification and systematical analyses of the genes associated with TPD are the prerequisites for elucidating the molecular mechanisms involved in TPD. The present study is undertaken to generate information about the genes related to TPD in rubber tree. RESULTS: To identify the genes related to TPD in rubber tree, forward and reverse cDNA libraries from the latex of healthy and TPD trees were constructed using suppression subtractive hybridization (SSH) method. Among the 1106 clones obtained from the two cDNA libraries, 822 clones showed differential expression in two libraries by reverse Northern blot analyses. Sequence analyses indicated that the 822 clones represented 237 unique genes; and most of them have not been reported to be associated with TPD in rubber tree. The expression patterns of 20 differentially expressed genes were further investigated to validate the SSH data by reverse transcription PCR (RT-PCR) and real-time PCR analysis. According to the Gene Ontology convention, 237 unique genes were classified into 10 functional groups, such as stress/defense response, protein metabolism, transcription and post-transcription, rubber biosynthesis, etc. Among the genes with known function, the genes preferentially expressed were associated with stress/defense response in the reverse library, whereas metabolism and energy in the forward one. CONCLUSIONS: The genes associated with TPD were identified by SSH method in this research. Systematic analyses of the genes related to TPD suggest that the production and scavenging of reactive oxygen species (ROS), ubiquitin proteasome pathway, programmed cell death and rubber biosynthesis might play important roles in TPD. Therefore, our results not only enrich information about the genes related to TPD, but also provide new insights into understanding the TPD process in rubber tree.
Assuntos
Regulação da Expressão Gênica de Plantas , Genes de Plantas/genética , Hevea/genética , Hevea/metabolismo , Látex/metabolismo , Hibridização de Ácido Nucleico , Northern Blotting , DNA Complementar/genética , DNA Complementar/metabolismo , Etiquetas de Sequências Expressas , Perfilação da Expressão Gênica , Biblioteca Gênica , Hevea/crescimento & desenvolvimento , Dados de Sequência Molecular , Reprodutibilidade dos TestesRESUMO
A rubber particle protein with apparent molecular mass of 43 kD as determined by SDS-PAGE was purified. A degenerate oligonucleotide primer based on the N-terminal amino acid sequence of this purified protein was used to amplify a 1385 bp cDNA by 3' rapid amplification of cDNA ends (3'RACE). The cDNA contains five repeats in a head-to-tail arrangement without intervening sequences, each encoding a ubiquitin unit of 76 amino acids. The last ubiquitin unit is followed by an extraphenylanaline residue at the carboxyl-terminal end. The structure of the cDNA is consistent with the structure of other known polyubiquitin genes. Western blot demonstrated that 43 kD rubber particle protein might be a polyubiquitin. Southern blot analysis revealed that there were multiple copies of gene encoding 43 kD rubber particle protein in Hevea brasiliensis. The results of Northern blot analysis indicated that the gene was expressed in latex, young leaves and bark tissue.
Assuntos
Hevea/química , Proteínas de Membrana/genética , Proteínas de Plantas/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , DNA Complementar/química , Dosagem de Genes , Proteínas de Membrana/química , Dados de Sequência Molecular , Peso Molecular , Proteínas de Plantas/químicaRESUMO
TPD (tapping panel dryness) is a complex physiological syndrome widely found in rubber tree (Hevea brasiliensis) plantations, which causes severe yield and crop losses in natural rubber-producing countries. The molecular mechanism underlying TPD is not known and there is presently no effective prevention or treatment for this serious disease. To investigate the molecular mechanism of TPD, we isolated and characterized genes for which the change of expression is associated with TPD. We report here the identification and characterization of a Myb transcription factor HbMyb1. HbMyb1 is expressed in leaves, barks, and latex of rubber trees, but its expression is significantly decreased in barks of TPD trees. Our results suggest that the expression of HbMyb1 is likely associated with TPD and that the function of HbMyb1 is associated with the integrity of bark tissue of rubber trees.