Transcriptome profiling of PeCRY1 transgenic Populus tomentosa

OsCRY2 and OsFBO10 co-regulate photomorphogenesis and photoperiodic flowering in indica rice

Cryptochromes (CRYs) are a class of photoreceptors that perceive blue/ultraviolet-A light of the visible spectrum to mediate a vast number of physiological responses in bacteria, fungi, animals and plants. In the present study, we have characterized OsCRY2 in a photoperiod sensitive indica variety, Basmati 370, by generating and analyzing overexpression (OE) and knock-down (KD) transgenic lines. The OsCRY2^OE lines displayed dwarfism as shown in their reduced plant height and leaf length, attributed largely by an overall reduction in their cell size. The OsCRY2^OE lines flowered significantly earlier and showed shorter and broader seeds with an overall reduced seed weight. The OsCRY2^KD lines showed contrasting phenotypes, such as increased plant height and delayed flowering, however, decreased seed size and weight were also observed in the KD lines, along with reduced spikelet fertility and high seed shattering rate in mature panicles. Novel interactions were confirmed between OsCRY2 and members of ZEITLUPE family of blue/ultraviolet-A light photoreceptors, encoded by OsFBO8, OsFBO9 and OsFBO10 which are orthologous to ZEITLUPE (ZTL), LOV KELCH PROTEIN2 (LKP2) and FLAVIN BINDING, KELCH REPEAT F-BOX1 (FKF1), respectively, of Arabidopsis thaliana. Since FKF1 is known to play a role in regulating photoperiodic flowering, OsFBO10 was chosen for further studies. OsCRY2 and OsFBO10 interacted in the nucleus and cytoplasm of the cell and cross-regulated the expression of each other. They were also found to regulate the expression of several genes involved in photoperiodic flowering in rice. Both OsCRY2 and OsFBO10 played a positive role in photomorphogenic responses in different light conditions. The physical interaction of OsCRY2 with OsFBO10, their involvement in common physiological and developmental pathways and their cross-regulation of each other suggest that the two photoreceptors may regulate common developmental pathways in plants, either jointly or redundantly.

Developing Portulaca oleracea as a model system for functional genomics analysis of C4/CAM photosynthesis

Previously regarded as an intriguing photosynthetic curiosity, the occurrence of C4 and Crassulacean acid metabolism (CAM) photosynthesis within a single organism has recently emerged as a source of information for future biotechnological use. Among C4/CAM facultative species, Portulaca oleracea L. has been used as a model for biochemical and gene expression analysis of C4/CAM under field and laboratory conditions. In the present work, we focussed on developing molecular tools to facilitate functional genomics studies in this species, from the optimisation of RNA isolation protocols to a method for stable genetic transformation. Eleven variations of RNA extraction procedures were tested and compared for RNA quantity and quality. Also, 7 sample sets comprising total RNA from hormonal and abiotic stress treatments, distinct plant organs, leaf developmental stages, and subspecies were used to select, among 12 reference genes, the most stable reference genes for RT-qPCR analysis of each experimental condition. Furthermore, different explant sources, Agrobacterium tumefaciens strains, and regeneration and antibiotic selection media were tested in various combinations to optimise a protocol for stable genetic transformation of P. oleracea. Altogether, we provide essential tools for functional gene analysis in the context of C4/CAM photosynthesis, including an efficient RNA isolation method, preferred reference genes for RT-qPCR normalisation for a range of experimental conditions, and a protocol to produce P. oleracea stable transformants using A. tumefaciens.

Transcriptome analysis of diploid and triploid Populus tomentosa

Triploid Chinese white poplar (Populus tomentosa Carr., Salicaceae) has stronger advantages in growth and better stress resistance and wood quality than diploid P. tomentosa. Using transcriptome sequencing technology to identify candidate transcriptome-based markers for growth vigor in young tree tissue is of great significance for the breeding of P. tomentosa varieties in the future. In this study, the cuttings of diploid and triploid P. tomentosa were used as plant materials, transcriptome sequencing was carried out, and their tissue culture materials were used for RT-qPCR verification of the expression of genes. The results showed that 12,240 differentially expressed genes in diploid and triploid P. tomentosa transcripts were annotated and enriched into 135 metabolic pathways. The top six pathways that enriched the most significantly different genes were plant-pathogen interaction, phenylpropanoid biosynthesis, MAPK signalling pathway-plant, ascorbate and aldarate metabolism, diterpenoid biosynthesis, and the betalain biosynthesis pathway. Ten growth-related genes were selected from pathways of plant hormone signal transduction and carbon fixation in photosynthetic organisms for RT-qPCR verification. The expression levels of MDH and CYCD3 in tissue-cultured and greenhouse planted triploid P. tomentosa were higher than those in tissue-cultured diploid P. tomentosa, which was consist ent with the TMM values calculated by transcriptome.