Project description:The cold acclimation process is regulated by many factors like ambient temperature, day length, light intensity, or hormonal status. Experiments with plants grown under different light-quality conditions indicate that the plant response to cold is also a light-quality-dependent process. Here, the role of light quality in the cold response was studied in one-month-old Arabidopsis thaliana (Col‐0) plants exposed for one week to 4 °C at short‐day conditions under white (100 and 20 μmol m‐2s‐1), blue or red (20 μmol m‐2s‐1) light conditions. An upregulated expression of CBF1, an inhibition of photosynthesis, and an increase in membrane damage showed that blue light enhanced the effect of low temperature. Interestingly, cold-treated plants under blue and red light showed only limited freezing tolerance compared to white light cold-treated plants. Next, the specificity of the light quality signal in cold response was evaluated in Arabidopsis accessions originating from different and contrasting latitudes. In all but one Arabidopsis accessions, blue light increased the effect of cold on photosynthetic parameters and electrolyte leakage. This effect was not found for Ws-0, which lacks functional CRY2 protein, indicating its role in the cold response. Proteomics data confirmed significant differences between red and blue light treated plants at low temperature and showed that the cold response is highly accession specific. In general, blue light increased mainly the cold-stress related proteins and red light induced higher expression of chloroplast-related proteins, which correlated with higher photosynthetic parameters in red light cold-treated plants. Altogether, our data suggest that light modulates two distinct mechanisms during the cold treatment - red light driven cell function maintaining program and blue light activated specific cold response. The importance of mutual complementarity of these mechanisms was demonstrated by significantly higher freezing tolerance of cold-treated plants under white light.

Project description:There are 16 organ samples (dry seeds, 24H imbibed seeds, 48H imbibed seeds, juvenile rosette, adult rosette, senescence leaves, cauline leaves, stems, young buds, mature flower buds, flowers, young siliques, mature siliques and old siliques) with triplicates. There are 17 samples of different environmental samples (0 h white, 1 h white, 6 h white, 24 h white, dark, blue, far-red and red lights, control, cold 2h, cold 6h, hot 2h, hot 6h, NaCl 2h, NaCl 6h, dry 2h and dry 6h) with triplicates. For 12 organs, three lines of plants were grown in soil under the long-day conditions of 16 hours light at 22℃. Samples were collected from each of juvenile rosette leaves, adult rosette leaves, cauline leaves, stems, young flower buds (sepals were closed and petals are not visible), mature flower buds (petals are visible), flowers, young siliques filled with white seeds, mature siliques filled with green seeds, old yellowing siliques (2-month-old) and senescence rosettes. Root tissues were collected from 2-week-old plants growing on 1% agar plates containing Murashige and Skoog (MS). Callus were collected from cultured CIM (callus induction medium) containing B5 medium supplemented with 20 g liter–1 glucose, 0.5 mg liter–1 2,4-D, and 0.1 mg liter–1 kinetin. Dry seed was defined to be after-ripened seeds for 4 weeks. Imbibed seeds are collected from seeds imbibed on the moistened paper for 24 and 48 hours under the continuous light at 22℃. In light irradiations, wild type (WT) seeds were plated on MS plates. For the time course experiment of white light, the plates were placed at 4°C in darkness for at least 2 days prior to receiving 6 h red light irradiation to synchronize germination. Then, plates were placed in the dark for 3 days and then exposed to white fluorescent light (100 μmol m–2 s–1) for 1, 6 and 24 h. For monochromatic light experiment, WT seedlings were grown in continuous red light, blue light, far-red light, or darkness for 6 days after red light irradiation. The light intensity used was 0.17 μmol m–2 s–1 for red light, 1.16 μmol m–2 s–1 for blue light and 0.53 μmol m–2 s–1 for far-red light. All abiotic stress samplings were collected from plants grown for 2 weeks on MS plates under 2 and 6 hours of abiotic stress conditions at the continuous light at 22℃. For drought stress treatment, plants were transferred and dehydrated onto the dried filter paper in the covered plastic dishes. For heat and cold stress treatments, the covered plastic dishes with plants were transferred directly from 22 to 37 and 2℃ respectively. For salinity stress treatment, plants were transferred onto the filter paper moistened with MS plates including 200mM NaCl.

Project description:Orchid Dendrobium Sonia (Sonia) has wide demand in floral market throughout the world due to its vibrant coloured flowers, flowering recurrence and dense inflorescence. Effects of different monochromatic light qualities (red, far-red, blue, white) on different developmental and growth responses such as seed gemination, shoot and root growth, chlorophyll and carotenoid accumulation were studied in Sonia. Asymbiotic seed germination was the highest under blue or white light (80%, p<0.001) and least under far-red (55%, p<0.001) suggesting that it could either be controlled by an exceptional novel function of Cryptochrome 1 or the blue wavelengths perceived by PHYA or PHYB in Sonia. All analyses were done in 6-months-old plants till 1 year of age. Shoot length increased significantly in white or red light (3.7-fold, 3.5-fold respectively) while was least under far-red (decreased by 1.6-fold) indicating the major regulatory role of PHYB for shoot growth. Root growth in red in Sonia was more similar to hypocotyl adventitious root (HAR) formation genetically considering PHYB transcript expression. We suggest that the root growth (HAR) under red in Sonia is partly attributed to PHYB, negatively regulated with HY5 transcription factor and positively associated with auxin biosynthesis and accumulation gene BABY BOOM (BBM2) and efflux carriers such as LIKE AUXIN RESISTANT 2 and 3 (LAX2, LAX3). Highest chlorophyll content under far-red and blue might be a hyper-response of SAR under FR light in Sonia. Taxonomic tree analysis finds Sonia closer to Phalenopsis and Dendrobium catenatum Lindl. The three phytochromes and one cryptochrome sequences which were similar to PHYA, B, C and CRY1 respectively. CRY1 was retrieved with one more isoform CRY1_X2, with all these sequences more similar to those of Oryza.sativa. Further study can clarify the indicating reason of a probable gene loss which is evident from the absence of any sequence similar to CRY2 in root RNA isolates of Dendrobium Sonia.

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