温度和光照对缘管浒苔光合作用的短期交互影响

Short-term interaction of temperature and light intensity on photosynthesis of green alga Ulva linza

为研究温度和光照对缘管浒苔Ulva linza光合作用的短期交互影响,设置了不同温度和光照交互作用藻体24 h的试验,试验设置30℃(高温)、20℃(最适温度,对照)、4℃(低温)3个温度组,在每个温度下设置400μmol/(m^(2)·s)(高光照)、100μmol/(m^(2)·s)(最适光照,对照)和20μmol/(m^(2)·s)(低光照)3个光照度,试验结束时进行了转录组学测序和光合荧光参数的测定。结果表明:试验周期内,缘管浒苔光合作用相关基因的表达变化受温度的影响大于光照,30℃和4℃下藻体的差异表达基因更多,其中,碳同化相关酶基因表达情况变化较大;短期高温和高光照处理对缘管浒苔具有协同胁迫作用,在高温高光照处理下,藻体的光化学效率(F_(v)/F_(m))显著下降且差异表达基因最多,其中,光合固碳相关差异基因表达显著下调(P<0.01);低光照处理提高了缘管浒苔对低温的耐受性,此条件下藻体的F_(v)/F_(m)显著高于单一低温下;在低温低光照处理下,缘管浒苔可能存在特殊的响应机制,藻体特异表达大量Unigene,其中,位于叶绿体的40S核糖体蛋白S24-1、S8-1及60S核糖体蛋白L12-1相关基因表达极显著上调(P<0.01|log_(2) (Fold Change) |>2),差异表达的捕光色素蛋白基因和电子传递链相关基因也显著上调(P<0.01)。研究表明,温度和光照对缘管浒苔光合作用具有协同作用,短期内高温高光照的协同作用会加剧藻体受到的胁迫,而低温低光照的协同作用有利于缓解藻体受到的胁迫。

In order to evaluate the short-term interaction of temperature and light intensity on photosynthesis in green alga Ulva linza, transcriptome sequencing and photosynthetic fluorescence parameters were determined in green alga in VSE culture medium exposed to temperature of 30 ℃(high temperature), 20 ℃(optimal temperature, as the control) and 4 ℃(low temperature) and light intensity of 400 μmol/(m^(2)·s)(high intensity), 100 μmol/(m^(2)·s)(optimal intensity, as control) and 20 μmol/(m^(2)·s)(low intensity). The results showed that the expression of the green alga genes was more affected by temperature than light intensity, with more differentially expressed genes at 30 ℃ and 4 ℃, when the gene expression of carbon assimilation-related enzymes changed greatly. There was short term synergistic stress of high temperature and high light intensity on the green alga, with significant decrease in F_(v)/F_(m)in all groups, with the down regulated photosynthetic carbon fixation in most differentially expressed related genes. Low light led to improve the tolerance of the green alga to low temperature(20 μmol/(m^(2)·s)), and significantly higher F_(v)/F_(m)than that under single low temperature(P<0.01). It was found that under low temperature and low light the green alga had special mechanism that a large number of unigenes were specifically expressed. The 40S ribosomal protein S24-1, S8-1 and 60S ribosomal protein L12-1 located in chloroplast were shown to be significantly up-regulated(P<0.01 and |log_(2) (Fold Change) |>2), as well as the differentially expressed genes related to light harvesting protein and electron transfer chain. The findings indicated that temperature and light intensity showed a synergistic effect on photosynthesis of the green aga: the synergistic effect of high temperature and high light aggravated the stress of alga, and that the synergistic effect of low temperature and low light alleviated the effect of the alga.