Genes differentially expressed under high irradiance (HI) stress in mature flag leaves of super-hybrid rice Liangyoupeijiu (Oryza sativa ssp. indica) were studied by the silver-staining mRNA differential display technique. We obtained 167 differentially displayed bands on silver-stained polyacrylamide gels and searched for their genetic origins. Five cDNA fragments, which were upregulated by HI stress, were cloned and sequenced. The clones of G25×320, A31×380, and G29×280 putatively encode a cytosolic monodehydroascorbate reductase (MDAR), a phosphatidylinositol 4-kinase (PI-4-K), and a DEAH-box RNA helicase, respectively. Most differentially expressed genes in hybrid rice were inherited from parents and many of them were related with both parents, although some were derived from one parent only. The differentially expressed cDNA fragments having no distinct genetic origins indicated the involvement of some unclear mechanisms in the inheritance processes from parents to hybrid. and G.-Q. Jiang ... [et al.].
The photoprotection of energy dissipation and water-water cycle were investigated by comparing chilling sensitivity of photosystems 2 (PS2) and 1 (PS1) in two chilling-sensitive plants, cucumber and sweet pepper, upon exposure to 4 °C under low irradiance (100 μmol m-2 s-1) for 6 h. During chilling stress, the maximum photochemical efficiency of PS2 (Fv/Fm) decreased only slightly in both plants, but the oxidisable P700 decreased markedly, which indicated that PS1 was more sensitive to chilling treatment under low irradiance than PS2. Sweet pepper leaves had lower Fv/Fm, higher non-photochemical quenching (NPQ), and higher oxidisable P700 during chilling stress. Activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in cucumber leaves was higher, but APX activity decreased apparently compared to that at room temperature. The productions of active oxygen species (H2O2, O2 -) increased in both plants, faster in cucumber leaves than in sweet pepper leaves. In sweet pepper leaves, a stronger de-epoxidation of the xanthophyll cycle pigments, a higher NPQ could act as a major protective mechanism to reduce the formation of active oxygen species during stress. Thus sensitivity of both plants to chilling under low irradiance was dominated by the protective mechanisms between PS1 and PS2, especially the energy dissipation and the water-water cycle. and X.-G. Li ... [et al.].