A comparative phenotypic study between bl2 and spl6 mutant wasperformed to characterize spot formation mechanisms of bl2 mutant. Small spots appeared at the seedling stage in bl2 and later it covered large round areas on the leaves whereas, relatively small red spots in parallel line on both leaf surfaces at late tillering stage were observed in spl6. Vegetative and reproductive growth was reduced due to lesion formation at early age in the mutants. Lower growth habit and agronomic trait value was observed in mutants as compared to wild type plants. Genetic segregation data among F2 population revealed that both mutants are recessive in nature. Mesophyll chloroplast was not found in spotted area which demonstrates the damage of chloroplast cell at spotted area due to cell death. Transmission electron microscopy also confirmed the chloroplast damage. Increased level of total chlorophyll and hydrogen peroxide content were observed till 45 days of growth after transplantation under natural environment and dropped at 60 days. Catalase activity was increased until 45 days and decreased at 60 days whereas very slight level difference in protein content was observed. However, increasing level of total ascorbic acid contents were found in spl6 and bl2 as compared with wild type till 60 days after transplantation. Higher expressions of OsPDI and OsGPX1 in bl2 spotted leaves were found whereas OsTPX expression was very low in the spotted leaf. (This research was supported by the National Research foundation of Korea, Grant 0070065).

Rice with purple colored pericarp deposit anthocyanin on the seed coat and color accumulation increased rapidly during seed development. The purple color of rice pericarp is genetically determined by the Prp locus. Inheritance of purple pericarp was studied in Prp/ Kumgangbyeo (indica type Korean variety). Pericarp color of the F1 plants was purple and the F2 population of 274 plants segregated into 3 purple: 1 white ratio indicating dominant nature of the purple color. Comparative proteomic approaches using 2-DE were applied to analyze the protein profiles and molecular mechanism of purple color formation in ricepericarp. Results revealed that approximately 1,500protein spots were reproducibly detected in the gels with silver staining across the two biological replicates. Among them, 46 proteins were expressed differentially between purple color pericarp rice and white color pericarp of the wild type rice, in which 28 and 16 protein spots were more than two fold up regulated in the wild type and purple pericarp, respectively. MALDI-TOF MS analysis of nine spots revealed that putative fructokinase,embryo-specific protein and one unknown proteins were abundant in the wild type, whereas, anthocyanidin synthase, putative chloroplast inner envelope protein, and dihydroflavonol reductase were highly abundant in the Prp rice. Results indicated anthocyanidin synthase and/or dihydroflavonol reductase might be involved in the biosynthetic pathway of the purple color formation in the rice pericarp. [This research was supported by the Grant funded by Agricultural R&D Promotion Center, ARPC (IPET project number: 108091-05-1-CG000)].

Rice lax panicle (lax) mutant had defect in early inflorescence differentiation and lateral branch formation and exhibitedfewer numbers of rachis branches and spikelets in the panicle. The mutant also had abnormality in floral organ formation. Whereas, the spotted leaf 6 (spl6) mutant produced lesions in absence of pathogen. Analysis with a lax spl6 double mutant indicated both genes are controlled by single recessive factor and linked on chromosome 1 with 7 centiMorgan map distance. The lax gene was fine mapped within the 261.3 kb region between RM7594 and RM5389 that predicted 10 open reading frames (ORF) as candidate for lax gene. Sequencing of the candidates in the lax mutant revealed a substitution of nucleotide T by G corresponding to an amino acid substitution from serine (S) to alanine (A) at the 117th position within the coding region of the candidate ORF bhlh123. The intronless 1080 bp cDNA of LAX gene contains an ORF of 215 amino acids and encoded a basic helix-loop-helix transcription factor. Analysis of a 5.1 kb genomic fragment of the lax gene from homozygous dominant progeny which corresponded to indica cultivar resulted in a long deletion of 24 nucleotides in the upstream of LAX cDNA. (This research was supported by the National Research foundation of Korea, Grant 0070065).

We have discussed here the phenotypic and genetic characteristics as well as proteomic analysis of lesion mimic mutants (LLM) in rice. LLM is one of the mutants that induces cell death without infection of pathogen and produces defense signaling pathways. As the phenotypic expression, most LLMs induce spots on the leaf blades and leaf sheaths at their various developmental stages. We have discussed the nature of bl1, bl2, spl1, spl3, spl4, spl5 and spl6 LLMs in rice which were formed developmentally controlled spot on the leaf blades that were appeared as tiny dotted spots during tillering stage and gradually increased up to maturity. Through Northern blot analysis lower levels of rubisco large subunit and rubisco small subunit were observed in spotted leaves (sp) compared to non-spotted leaves (nsp). However, catalase was severely degraded in the sp. Broken thylakoid membranes of mesophyll chloroplasts were seen in nsp sections and were absent in sp sections of the mutant. Through 2-DE analysis 159 protein spots were differentially expressed between wild type and mutant from identified 800 reproducibleproteins, where 114 spots were up-regulated and 45 were down-regulated. Among quantified 25 protein spots, except two, all of the protein spots including protein disulfide isomerase, transketolase, thioredoxin peroxidase, ATP synthase, and rubisco large and small subunits were identified in the wild type but were absent in the mutant. However, catalase was up-regulated in the mutant. Genetic analysis indicated that studied bl1, bl2 and spl6 mutants are controlled by a single recessive gene.