Project description:Rhododendron hybridum Hort. (Ericaceae) is an important ornamental species with striking continuous flowering feature. However, few genomic resources are currently available in this species, and the breeding programs were handicapped by the lack of basic genetic information. Here, we established a transcriptomic profiling study from four different tissues using RNA-Seq to gain insight on the functional genes and to isolate EST-SSR markers for breeding and conservation purposes. In total 38,050,296 high-quality sequence reads were obtained, and 56,120 unigenes (with N50 = 1,236bp) were assembled. Of which, 32,580 (58.05 %) and 8,788 (15.66 %) were annotated to GO and KEGG database, respectively. Additionally, 38,775 (69.09 %) and 37,409 (66.66 %) R. hybridum unigenes were aligned to the Arabidopsis thaliana and Oryza sativa genome, respectively. A total of 21,103 simple sequence repeat (SSR) motifs were identified in 15,050 contigs. Among them, dinucleotide repeats account for the largest proportion for 49.27%, followed by mono- (35.94%) and trinucleotide (21.5%). This study represents the first transcriptome data of R. hybridum and confirms that the transcriptome assembly data are a useful resource for EST-SSR loci development. Such vast sequence data and markers will be robust tools for genomic research and breeding of R. hybridum and related species.
Project description:Rhododendron is well known woody plant, as having high ornamental and economic values. Heat stress is one of the important environmental stresses that effects Rhododendron growth. Recently, melatonin was reported to alleviate abiotic stress in plants. However, the role of melatonin in Rhododendron is still unknown. In the present study, the effect of melatonin on Rhododendron under heat stress and the potential mechanism was investigated. Through morphological characterization and chlorophyll a fluorescence analysis, 200µM was selected for the best melatonin concentration to mitigate heat stress in Rhododendron. To reveal the mechanism of melatonin priming alleviating the heat stress, the photosynthesis indexes, Rubisco activity and ATP content were detected in 25 ℃, 35 ℃ and 40 ℃. The results showed that melatonin improves electron transport rate (ETR), PSII and PSI activity, Rubisco activity and ATP content under high temperature stress. Furthermore, transcriptome analysis showed that a significant enrichment of differentially expressed genes in the photosynthesis pathway, and most of genes in photosynthesis pathway displayed a more significantly slight down-regulation under high temperature stress in melatonin-treatment plants, compared with melatonin-free plants. We identified PGR5……Together, these results demonstrate that melatonin could promote the photosynthetic electron transport, improve the enzymes activities in Calvin cycle and the production of ATP, and thereby increase photosynthetic efficiency and CO2 assimilation capacity under heat stress, through regulating the expression of some key genes, such as PGR5…Therefore, melatonin application displayed great potential to cope with the heat stress in Rhododendron.
