UV-B对雨生红球藻生长及虾青素积累的影响

以雨生红球藻(Haematococcus pluvialis)为材料,研究不同强度的UV-B对雨生红球藻生长、光合作用及虾青素积累的影响和其作用机理。设置5种紫外线强度,分别在正常光照培养条件下补充不同强度UVB(100—500 lx),标记为CK、U100、U200、U300、U400和U500六组。结果表明,经UV-B辐射后雨生红球藻细胞密度、PSⅡ最大光化学效率(F_v/F_m)、非光化学淬灭系数(NPQ)和叶绿素(Chl.a和Chl.b)含量等均呈现下降趋势,且与辐射强度相关。相反,虾青素含量在100—400 lx强度下随UV-B辐射强度的增加而升高。与对照相比,高强度UV-B辐射(U400)36h和72h后藻细胞虾青素含量分别提高了35.68%和56.23%,达到5.82和7.06 mg/L。qRT-PCR检测发现雨生红球藻虾青素合成关键酶基因(IPI、PSY、BCH和BKT)的表达量随紫外辐射强度和辐射时间的增加均有不同程度升高。UV-B辐射亦调控紫外光受体UVR8及其信号转导通路核心元件(COP1、SPA1、HYH和HY5)的基因表...     

The Arabidopsis GAMYB-like genes, MYB33 and MYB65, are microRNA-regulated genes that redundantly facilitate anther development

The functions of the vast majority of genes encoding R2R3 MYB domain proteins remain unknown. The closely related MYB33 and MYB65 genes of Arabidopsis thaliana have high sequence similarity to the barley (Hordeum vulgare) GAMYB gene. T-DNA insertional mutants were isolated for both genes, and a myb33 myb65 double mutant was defective in anther development. In myb33 myb65 anthers, the tapetum undergoes hypertrophy at the pollen mother cell stage, resulting in premeiotic abortion of pollen development. However, myb33 myb65 sterility was conditional, where fertility increased both under higher light or lower temperature conditions. Thus, MYB33/MYB65 facilitate, but are not essential for, anther development. Neither single mutant displayed a phenotype, implying that MYB33 and MYB65 are functionally redundant. Consistent with functional redundancy, promoter-beta-glucuronidase (GUS) fusions of MYB33 and MYB65 gave identical expression patterns in flowers (sepals, style, receptacle, anther filaments, and connective but not in anthers themselves), shoot apices, and root tips. By contrast, expression of a MYB33:GUS translational fusion in flowers was solely in young anthers (consistent with the male sterile phenotype), and no staining was seen in shoot meristems or root tips. A microRNA target sequence is present in the MYB genes, and mutating this sequence in the MYB33:GUS fusion results in an expanded expression pattern, in tissues similar to that observed in the promoter-GUS lines, implying that the microRNA target sequence is restricting MYB33 expression. Arabidopsis transformed with MYB33 containing the mutated microRNA target had dramatic pleiotrophic developmental defects, suggesting that restricting MYB33 expression, especially in the shoot apices, is essential for proper plant development.