Project description:Sucrose is the major product of photosynthesis in many higher plants. It is transported from the source tissue through the phloem to various sink tissues to support plant growth, development and reproduction. Knowledge of the signal transduction pathways involved in carbohydrate metabolism is limited. Genes involved in the regulation of sucrose synthesis and accumulation could be used as tools in the development of genetically manipulated plants with higher sucrose content or aid in breeding programs as molecular markers. Using the SUCEST (Sugarcane EST) database information and a microarray approach, the expression profiles of 1920 sugarcane (Saccharum spp.) genes encoding signal transduction elements, transcription factors and stress-related proteins were analyzed. In order to assess their involvement in sucrose metabolism, the expression profiles of individuals from a sugarcane population segregated for sugar content were compared. From a population of 500 F1 individuals, the seven with the highest and the seven with the lowest sugar contents were selected, pooled and profiled using cDNA microarrays. Twenty-four genes were identified as differentially expressed. Five of them were more expressed in the plants with the highest sugar contents and 19 in the plants with the lowest sugar contents. RNA-blot hybridization was used to validate the expression profiles obtained for individuals in each group. These genes were shown to have differential expression throughout the growing season and in the different tissues. Our data supports the view that sugar levels modulate a complex signal transduction network that seems to involve responses related to stress. Keywords: Segregated population
Project description:Sugarcane established industrial crop providing sugar, ethanol and biomass-derived electricity around the world. Cane sugar content is an important, breeding target, but its improvement remains very slow in many breeding programmes. Biotechnology strategies to improve sucrose accumulation made little progress at crop level, mainly due to the limited understanding of its regulation. MiRNAs regulate many metabolic processes in plants. However, their roles and target genes associated with sugarcane sucrose accumulation remains unknown. Here, we conducted high-throughput sequencing of transcriptome, small RNAs and degradome of leaves and stem of two sugarcane genotypes with contrasting sucrose content from the early to late stages of sucrose accumulation stages, which provided more insights into miRNA-associated gene regulation during sucrose accumulation. Transcriptome analysis identified 18,722 differentially expressed genes (DEGs) between both genotypes during sucrose accumulation. The major DEGs identified were involved in starch and sucrose metabolism, and photosynthesis etc. miRNA sequencing identified 563 known and 281 novel miRNAs from both genotypes during sucrose accumulation. Of these, 311 miRNAs were differentially expressed.752 targets of 368 miRNAs (609 targets for 260 known miRNAs and 168 targets for 108 novel miRNAs) were identified by degradom sequencing.Several known and novel miRNAs and their target genes associated with sugar metabolism, sugar transport and sucrose storage were identified in this study.This new insight into the complex network of sucrose accumulation in sugarcane will help identify candidate targets for sucrose improvement in sugarcane through molecular means.
Project description:Background: Sugarcane is an important sugar and energy crop largely used for bioethanol production in the world. The development of sugarcane cultivars with high sucrose content and yield is one of the biggest challenges of breeding programs nowadays. To identify genes networks that underlie sucrose content and yield, we used a custom designed oligonucleotide array with 21,901 different probes to study the transcriptome from breeding populations of sugarcane contrasting to sucrose content and genotypes contrasting to photosynthesis rate. Results: Physiological and biochemical data reveals that the transcriptome profiles described here showed a close relationship between sucrose content and stem development. A total of 2135 genes were differentially expressed in at least one experimental hybridization. We identified genes related to carbohydrate metabolism, cell wall metabolism and signal transduction. The same oligoarrays was used to detect transcription in both sense and antisense orientation. The enriched functional category from antisense expressed genes reveals light harvesting and circadian clock as the two top categories that can be related to photosynthesis and yield in sugarcane. Conclusions: Knowledge on the mechanisms underlying carbon partitioning and its relationship with sucrose accumulation in sugarcane stems would help defines routes to increase yield. Our findings showed for instance that sucrose accumulation and yield in sugarcane may be regulated by hormone signaling pathways, light harvesting and circadian clock genes. Analysis of the expression data and gene category enrichment provided an insight into signaling pathways and transcriptional control contrasting in high brix and low brix plants as well as differing photosynthesis rates and yield.