Regulation of the expression of ethylene biosynthesis genes in Hevea brasiliensis shoots

Montoro Pascal, Rio Maryannick, Leclercq Julie, Oliver Gérald, Sabau Xavier. 2009. Regulation of the expression of ethylene biosynthesis genes in Hevea brasiliensis shoots. In : 3rd IRRDB Workshop on the Hevea Genome and Transcriptome, 3-5 June, 2009, Montpellier, France. CIRAD, IFC, IRRDB. Montpellier : CIRAD, Résumé, 24-26. IRRDB Workshop on the Hevea Genome and Transcriptome. 3, Montpellier, France, 3 Juin 2009/5 Juin 2009.

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Résumé : Ethephon, an ethylene generator, is applied to the bark of rubber trees to increase natural rubber production by stimulating both latex flow and regeneration. A good command of both ethephon concentration and its frequency of application is required to avoid an oxidative burst into latex cells resulting in tapping panel dryness (TPD) and a loss of production. Although a little is known about the molecular response to ethylene stimulation further studies on ethylene biosynthesis and its regulation were needed to gain a better understanding of the mechanisms involved in latex production. The ethylene biosynthesis pathway is well characterised in many plant species. Sadenosyl- methionin (SAM) is produced from the methionin (Met) by the enzyme SAM synthase. Then, SAM is converted in 1-aminocyclopropane-1-carboxylic acid (ACC) by the ACC synthase (ACS) (Kende, 1993; Yang & Hoffman, 1984). ACC is converted to ethylene by the enzyme ACC oxidase, the production of which is also highly regulated. These three enzymes are encoded by a multigene family and their expression regulated differentially by various developmental, environmental and hormonal signals (Barry et al., 2000; Ge et al., 2000; Hacham et al., 2007; Llop-Tous et al., 2000) Several genes involved in the ethylene biosynthesis were previously isolated in rubber tree from cDNA library screening or PCR amplification of conserved regions using degenerated primers then RACE extension technology (Kuswanhadi, 2006). A differential gene expression was observed during plant development (Kuswanhadi et al., 2005) and a kinetic in response to ethephon, ethylene and wounding in 3-month-old budded plants (Kuswanhadi et al., 2006). In this study, we have monitored the expression of eight genes encoding four enzymes (SAMS, ACS, ACO and βCAS) by real-time RTPCR. These expression levels in bark tissues of budded plant 3-month-old flushes were compared from three Hevea clones with contrasting metabolism. The variation in gene expression depends on the clones and the genes. The accumulation of SAMS transcripts is dramatically increased in line with the decrease of the clone metabolism. In addition, this gene is induced during the daytime. ACS genes are poorly expressed in any clones. By contrast, ACO1 transcripts are accumulated in clone PB 260 and its gene is down-regulated during the daytime. ACO2 gene is more expressed at time 8 am in PB 217 than in other clones, and then induced during daytime. ACO3 gene is expressed at a very high level in PB 260. βCAS transcripts are accumulated in all clones and induced by the daytime in RRM 600 and PB 260.

Mots-clés Agrovoc : Hevea brasiliensis, éthylène

Mots-clés géographiques Agrovoc : France

Classification Agris : F30 - Génétique et amélioration des plantes
F62 - Physiologie végétale - Croissance et développement

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