Reduction in stratospheric ozone layer increases the amount of ultraviolet-B radiation (UVB: 280-320 nm) that reaches the earth ’ s surface. UVB radiationcan damage plants, resulting in decrease in growth and productivity. UVB-augmentation studies have indicated that the sensitivity to UVB radiation in plants varies among the species and cultivars. However. there are no definitive answers for the mechanisms of UVB-resistance in higher plants and for bioengineering design and development of UVB-tolerant plants. We have been studying physiological and biochemical aspects of the effects of UVB radiation on growth and yield of rice COryza sativa LJ. aiming to clarify the mechanism of resistance to UVB radiationin rice. At this meeting. weintroduce our research as followed: (1) supplementary UVB radiation has inhibitory effects on the growth. yield and grain development of rice; (2) UVB sensitivity of rice varies widely among cultivars; (3) among Japanese rice cultivars. Sasanishiki. a leading variety in northeast Japan. is more resistant to UVB. while Norin 1. a progenitor of Sasanishiki. is less resistant; (4)UV-sensitive Norin 1 cultivar is deficient in photorepair of UVB-induced cyclobutane pyrimidine dimer (CPD). and this deficiency results from one amino acid residue alteration of CPD photolyase. These results suggest that spontaneously occurring mutation in CPD photolyase gene could lead to difference in UVB sensitivity in rice. and that CPD photolyase might be a useful target for improving UVB-sensitivity in rice by selective breeding or bioengineering of UVB-tolerant rice.

To protect the watermelon against soil-borne pathogens, we are currently producing disease-resistant transgenic root stock for the growth of watermelon, A defensin gene (J1-1) from Capsicum annum, a ACC deaminase gene from Pseudomonas syringae, a galactinol synthase (CsGolS) gene from Cucumis sativus, and a WRKY (CvWRKY2) gene from Citullus vulgaris were used as transgenes for disease resistance. The gene were transformed into a inbred line (6-2-2) of watermelon, Kong-dae watermelon and a inbred line (GO702S) of gourd, respectively, by Agrobacterium-mediated transformation. Putative transgenic plants were selected in medium containing 100mg/L kanamycin, and then integration of the genes into the genomic DNA were demonstrated by PCR analysis. Successful integration of the gene in regenerated plants was also confirmed by PCR (Figf 1), genomic Southern blot (Fig 2), RT-PCR (Fig 3), and Northern blot analysis(Fig 4). Several T1 lines having different transgene were produced, and disease resistance of the T1 lines are under estimation.

Little is known about the effect of epigallocatechin-3 gallate (ESCG), a major constituent of green tea, on the expression of cyclooxygenase (COX)-2. Here, we studied the role of phospholipase D (PLD) isozymes in EGCG-induced COX-2 expression. Stimulation of human astrocytoma cells (U87) with EGCG induced formation of phosphatidylbutanol, a specific product of PLD activity, and synthesis of COX-2protein and its product, prostaglandin $E_2$ ($PGE_2$). Pretreatment of cells with 1-butanol, but not 3-butanol, suppressed EGCG-induced COX-2 expression and $PGE_2$ synthesis. Furthermore, evidence that PLD was involved in EGCG-induced COX-2 expression w3s provided by the observations that COX-2 expression was stimulated by over-expression of PLD1 or PLD2 isozymes and treatment with phosphatidic acid(PA), and that prevention of PA dephosphorylation by 1-propranolol significantly potentiated COX-2expression Induced by EGCG. EGCG induced activation of p38 mitogen-activated protein kinase (p38MAPK), and specific Inhibition of p38 MAPK dramatically abolished EGCG-Induced PLD activation, COX-2 expression, and $PGE_2$ formation. Moreover, protein kinase C (PKC) inhibition suppressed EGCG-induced p38 MAPK activation, COX-2 expression, and $PGE_2$ accumulation. The same pathways as those obtained in the astrocytoma cells were active in primary rat astrocytes, suggesting the relevance of the findings. Collectively, our results demonstrate for the first time that PLD isozymes mediate EGCG-induced COX-2 expression through PKC and p38 in immortalized astroglial line and normal astrocyte cells.

Sialic acid containing glycosphingolipids (gangliosides) have been implicated in the regulation of various biological phenomena such as atherosclerosis. Recent report suggeststhat exogenously supplied disialoganglioside (GD3) serves a dual role in vascular smooth muscle cells (VSMC) proliferation and apoptosis. However, the role of the GD3 synthase gene in VSMC responses has not yet been elucidated. To determine whether a ganglioside is able to modulate VSMC growth. the effect of overexpression of the GD3 synthase gene on DNA synthesis was examined. The results show that the overexpression of this gene has a potent inhibitory effect on DNA synthesis and ERK phosphorylation in cultured VSMC in the presence of PDGF. The suppression of the GD3 synthase gene was correlated with the down-regulation of cyclinE/CDK2. the up-regulation of the CDK inhibitor p21 and blocking of the p27 inhibition,whereas up-regulation of p53 as the result of GD3 synthase gene expression was not observed. Consistently, blockade of GD3 function with anti-GD3 antibody reversed VSMC proliferation and cell cycle proteins. The expression of the CD3 synthase gene also led to the inhibition of TNF--induced matrix metalloproteinase-9 (MMP-9) expression in VSMC as determined by zymography and immunoblot. Furthermore, GD3 synthase gene expression strongly decreased MMP-9 promoteractivlty in response to TNF-. This inhibition was characterized by the down-regulation of MMP-9,which was Iranscriptionally regulated at NF-B and activation protein-1 (AP-1) sites in the MMP-9promoter Finally, the overexpression of MMP-9 in GD3 synthase transfectant cells rescued VSMC proliferation. However MMP-2 overexpression was not affected the cell proliferation. These findings suggest that the fl13 synthase gene represents a physiological modulator of VSMC responses that may contribute to plaque instability in atherosclerosis.