Changes at the 3′-untranslated region stabilize Rubisco activase transcript levels during heat stress in Arabidopsis
Changes at the 3′-untranslated region stabilize Rubisco activase transcript levels during heat stress in Arabidopsis
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DOI：
10.1007/s00425-012-1623-0
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发表时间：
2012-08-01
期刊：
影响因子：
4.3
通讯作者：
Shapiro, Mariya B.
中科院分区：
文献类型：
--
作者：
DeRidder, Benjamin P.;Shybut, Mikel E.;Shapiro, Mariya B.
热胁迫对光合作用的抑制伴随着Rubisco伴侣活化酶（RCA）的功能受损，导致Rubisco失活。由于活化酶对热变性极其敏感，RCA在转录物或蛋白质水平上的表达变化可以提供光合作用对长期热胁迫的适应机制。使用定量实时PCR（qPCR），我们显示在拟南芥中的稳态RCA转录物水平在长时间暴露于中等热量（35 A摄氏度）期间是稳定的。RCA转录物的调查表明，热应激并没有改变编码活化酶的α和β-同种型的转录物的相对丰度，所述活化酶是通过前体mRNA的选择性剪接产生的。相反，在热应激植物中mRNA的稳定与活化酶3 '-非翻译区的平均长度的显著减少相一致，并且与未表征的活化酶mRNA剪接变体AtRCA β 2的富集相关。转录特异性qPCR结果表明，AtRCA β 2 mRNA在热胁迫下比AtRCA α和AtRCA β mRNA更稳定。使用诱导型转基因系统，我们发现缺乏天然3 '非翻译区的RCA转录物在体内比其全长对应物显著更稳定。使用该系统，在不存在RCA转录的情况下，在体内检查RCA蛋白质在24小时内的稳定性。在最佳和升高的温度下，RCA蛋白水平在缺乏RCA mRNA的植物中保持稳定，但当RCA mRNA存在时，特别是在热应激植物中，RCA蛋白水平增加。本研究揭示了一种可能的机制，涉及一个重要的光合作用调控基因的转录后调控，光合适应热胁迫。
Inhibition of photosynthesis by heat stress is accompanied by functional impairment of Rubisco's chaperone, activase (RCA), resulting in deactivation of Rubisco. Since activase is extremely sensitive to thermal denaturation, changes in expression of RCA at the transcript or protein level could provide a mechanism for acclimation of photosynthesis to prolonged heat stress. Using quantitative real-time PCR (qPCR) we show steady-state RCA transcript levels in Arabidopsis thaliana are stabilized during prolonged exposure to moderate heat (35 A degrees C). A survey of RCA transcripts indicates heat stress did not alter the relative abundance of transcripts encoding alpha and beta-isoforms of activase that are produced by alternative splicing of the pre-mRNA. Instead, mRNA stabilization in heat-stressed plants coincided with a significant reduction in the average length of activase 3'-untranslated regions, and was associated with enrichment of an uncharacterized activase mRNA splice variant, AtRCA beta 2. Transcript-specific qPCR revealed AtRCA beta 2 mRNA was more stable than AtRCA alpha and AtRCA beta mRNA in heat-stressed plants. Using an inducible transgenic system, we found that RCA transcripts lacking their native 3'-untranslated region were significantly more stable than their full-length counterparts in vivo. Using this system, stability of the RCA protein was examined over 24 h in vivo, in the absence of RCA transcription. At both optimal and elevated temperatures, RCA protein levels remained stable in plants lacking RCA mRNA, but increased when RCA mRNA was present, particularly in heat-stressed plants. This study reveals a possible mechanism, involving post-transcriptional regulation of an important photosynthesis regulatory gene, for acclimation of photosynthesis to heat stress.