Characteristic expression of twelve rice PR1 family genes in response to pathogen infection, wounding, and defense-related signal compounds (121/180)

Pathogenesis-related (PR) proteins have been used as markers of plant defense responses, and are classified into 17 families. However, precise information on the majority members in specific PR families is still limited. We were interested in the individual characteristics of rice PR1 family genes, and selected 12 putatively active genes using rice genome databases for expressed genes. All were upregulated upon compatible and/or incompatible rice-blast fungus interactions; three were upregulated in the early infection period and four in the late infection period. Upon compatible rice–bacterial blight interaction, four genes were upregulated, six were not affected, and one was downregulated. These results are in striking contrast to those among 22 ArabidopsisPR1 genes where only one gene was pathogen-inducible. The responses of individual genes to salicylic acid, jasmonic acid, and ethylene induced defense signaling pathways in rice are likely to be different from those in dicot plants. Transcript levels in healthy leaves, roots, and flowers varied according to each gene. Analysis of the partially overlapping expression patterns of rice PR1 genes in healthy tissues and in response to pathogens and other stresses would be useful to understand their possible functions and for use as characteristic markers for defense-related studies in rice

Characterization of a Maize Sucrose–phosphate Synthase Protein and Its Effect on Carbon Partitioning in Transgenic Rice Plants

We obtained transgenic rice (Oryza sativa L. cv. Nipponbare) plants with the gene for maize sucrose-phosphate synthase (EC 2.4.1.14, SPS). Some of the transgenic plants over-expressed maize SPS (over-expressing plants) and some had reduced levels of native SPS protein (co-suppressed plants). There was a positive correlation between the amounts of maize SPS protein and SPS activities. However, apparent Km values for uridine diphosphoglucose (UDPG) were higher in over-expressing plants than in control rice plants. These results suggest that overproduced maize SPS protein was not fully activated. The sucrose contents did not differ significantly between control and over-expressing rice plants, but they were lower in co-suppressed plants than in control plants. The starch contents were negatively and the sucrose/starch ratios were positively correlated with SPS activities. Thus, carbon partitioning in the transgenic rice was changed, even though rice is predominantly a sucrose-former

Elevated Sucrose-phosphate Synthase Activity in Source Leaves of Potato Plants Transrformed with the Maize SPS Gene

Sucrose-phosphate synthase (SPS) activity in source leaves of potato plants (Solanum tuberosum cv. May Queen) transformed with maize SPS gene under the control of a modified cauliflower mosaic virus (CaMV) 35S promoter was two to four times higher than the endogenous activity found in the control. A negative correlation (r = 0.82) between SPS activity and the ratio of starch to sucrose was observed. There were no significant changes in starch synthesis enzyme (ADGPase and QE) activities in the leaves. Photosynthesis did not differ significantly between control and transgenic lines. Aboveground (leaves and stem) and belowground (tuber) dry matter in three transgenic lines harvested during tuber development increased up to 15% and 20%, respectively, indicating that increased capacity for sucrose synthesis in potato leaves may lead to favorable growth. Moreover, the activity of this enzyme in source leaves of two transgenic potatoes increased when reaction temperature was elevated from 15°C to 35°3, a response similar to that of SPS in maize. Since temperature is a limiting factor for growth of potato, the transgenic plants will be useful for future studies under higher temperature growth conditions