Since global climate changes drastically, pre-harvest sprouting (PHS) is expected to pose serious problems in rice production. CBL-interacting serine/threonine protein kinases (CIPKs) have been implicated to play important role in regulating various abiotic stresses such as cold, salinity and drought. In this study, to understand the function of this gene under pre-harvest sprouting in rice, a cDNA clone encoding CBL-interacting protein kinase 15 was isolated from rice flowers. We constructed a recombinant vector carrying the CIPK15 under the control of the CaMV 35S promoter and Tnos terminator and transformed into rice using Agrobacterium tumefaciens. Insertion of the gene was verified in transformants using HPT resistance test and genomic PCR. Transcriptional profiling using tissues of wild type, Gopum, revealed expression of the gene in whole plant tissues with level of expression highest in the seeds suggesting possible role in dormancy. Comparative expression analysis of the gene in transgenic and wild type through semi-quantitative RT-PCR and real-time PCR showed higher expression in transgenic rice lines. Moreover, screening in the mist chamber showed overexpression lines that were resistant to the PHS. This result suggests the involvement of CIPK15 in the regulation of pre-harvest sprouting.

Fortification with vitamins in crops like rice is a continuing endeavor for geneticists and rice breeders. Tryptophan is one of the essential amino acids needed in human diet. In this study, we developed rice mutant lines using ethyl methane sulfonate (EMS) treatment in Korean cv. Donganbyeo and candidate rice lines were selected by insensitivity to the tryptophan analog, 5-methyltryptophan. One of the mutants has a 20-25 fold higher tryptophan level in mature seeds than wild type. To identify the mutations in anthranilate synthase genes, OASA1 and OASA2 sequences were generated. Moreover, mRNA expression levels of tryptophan biosynthesis related genes were examined. To further qualify the tryptophan fortification in rice, comparative assessment of cooking and eating quality was conducted with mutant lines and wild type. The moisture, viscosity, taste quality, protein content, amylose content and amino acid composition were similar with wild type. However, tryptophan contents in the mutant lines were higher than wild type as we targeted. The mutation present in AS gene of 5MT resistant rice may prove useful for the generation of crops with increased tryptophan contents and the mutation differences in AS sequences can be used for selection of mutant lines with high tryptophan level from large population.