Identification and characterisation of blue light photoreceptor gene family and their expression in tomato () under cold stress.

The Arabidopsis thaliana L. photoreceptor genes homologues in tomato (Solanum lycopersicum L.) genome were analysed using bioinformatic tools. The expression pattern of these genes under cold stress was also evaluated. Transcriptome analysis of the tomato sequence revealed that the photoreceptor gene family is involved in abiotic stress tolerance. They participate in various pathways and controlling multiple metabolic processes. They are structurally related to PAS, LIGHT-OXYGEN-VOLTAGE-SENSING (LOV), DNA photolyase, 5,10-methenyl tetrahydrofolate (MTHF), flavin-binding kelch F-box, GAF, PHY, Seven-bladed β-propeller and C27 domains. They also interact with flavin adenine dinucleotide (FAD), (5S)-5-methyl-2-(methylsulfanyl)-5-phenyl-3-(phenylamino)-3,5-dihydro-4H-imidazol-4-one (FNM) and Phytochromobilin (PϕB) ligands. These interactions help to create a cascade of protein phosphorylation involving in cell defence transcription or stress-regulated genes. They localisation of these gene families on tomato chromosomes appeared to be uneven. Phylogenetic tree of tomato and Arabidopsis photoreceptor gene family were classified into eight subgroups, indicating gene expression diversity. Morphological and physiological assessment revealed no dead plant after 4h of cold treatment. All the plants were found to be alive, but there were some variations in the data across different parameters. Cold stress significantly reduced the rate of photosynthesis from 10.06 to 3.16μmolm-2 s-1 , transpiration from 4.6 to 1.3mmolm-2 s-1 , and stomatal conductance from 94.6 to 25.6mmolm-2 s-1 . The cold stressed plants also had reduced height, root/shoot length, and fresh/dry biomass weight than the control plants. Relative expression analysis under cold stress revealed that after 4h, light stimulates the transcript level of Cry2 from 1.9 to 5.7 and PhyB from 0.98 to 6.9 compared to other photoreceptor genes.