Expression behaviour of primary carbon metabolism genes during sugarcane culm development

[摘要] ENGLISH ABSTRACT: Despite numerous attempts involving a variety of target genes, the successfultransgenic manipulation of sucrose accumulation in sugarcane remains elusive. It isbecoming increasingly apparent that enhancing sucrose storage in the culm bymolecular means may depend on the modification of the activity of a novel genetarget. One possible approach to identify target genes playing crucial coarseregulatory roles in sucrose accumulation is to assess gene expression during thedevelopmental transition of the culm from active growth to maturation. This studyhas resulted in the successful optimisation of a mRNA hybridisation technique tocharacterise the expression of 90 carbohydrate metabolism-related genes in threedevelopmentally distinct regions of sugarcane culm. A further goal of this work wasto extend the limited knowledge of the regulation of sucrose metabolism in sugarcane,as well as to complement existing data from physiological and biochemical studies.Three mRNA populations derived from the different culm regions were assayed andtheir hybridisation intensities to the immobilised gene sequences statisticallyevaluated. The relative mRNA transcript abundance of 74 genes from three differingregions of culm maturity was documented. Genes exhibiting high relative expressionin the culm included aldolase, hexokinase, cellulase, alcohol dehydrogenase andsoluble acid invertase. Several genes (15) were demonstrated to have significantlydifferent expression levels in the culm regions assessed. These included UDP-glucosepyrophosphorylase and UDP-glucose dehydrogenase, which were down-regulatedbetween immature and mature internodes. Conversely, sucrose phosphate synthase,sucrose synthase and neutral invertase exhibited up-regulation in maturing internodaltissue. A variety of sugar transporters were also found to be up-regulated in matureculm, indicating a possible control point of flux into mature stem sink tissues.Combined with knowledge of the levels of key metabolites and metabolicintermediates this gene expression data will contribute to identifying key controlpoints of sucrose accumulation in sugarcane and assist in the identification of genetargets for future manipulation by transgenic approaches.

[发布机构] Stellenbosch University