Suganami Mao, Suzuki Yuji, Tazoe Youshi, Yamori Wataru, Makino Amane
Graduate School of Agricultural Science, Tohoku University, Sendai 980-8572, Japan.
Faculty of Agriculture, Iwate University, Morioka, Iwate 020-8550, Japan.
Plant Physiol. 2021 Feb 25;185(1):108-119. doi: 10.1093/plphys/kiaa026.
Rubisco limits C3 photosynthesis under some conditions and is therefore a potential target for improving photosynthetic efficiency. The overproduction of Rubisco is often accompanied by a decline in Rubisco activation, and the protein ratio of Rubisco activase (RCA) to Rubisco (RCA/Rubisco) greatly decreases in Rubisco-overproducing plants (RBCS-ox). Here, we produced transgenic rice (Oryza sativa) plants co-overproducing both Rubisco and RCA (RBCS-RCA-ox). Rubisco content in RBCS-RCA-ox plants increased by 23%-44%, and RCA/Rubisco levels were similar or higher than those of wild-type plants. However, although the activation state of Rubisco in RBCS-RCA-ox plants was enhanced, the rates of CO2 assimilation at 25°C in RBCS-RCA-ox plants did not differ from that of wild-type plants. Alternatively, at a moderately high temperature (optimal range of 32°C-36°C), the rates of CO2 assimilation in RBCS-ox and RBCS-RCA-ox plants were higher than in wild-type plants under conditions equal to or lower than current atmospheric CO2 levels. The activation state of Rubisco in RBCS-RCA-ox remained higher than that of RBCS-ox plants, and activated Rubisco content in RCA overproducing, RBCS-ox, RBCS-RCA-ox, and wild-type plants was highly correlated with the initial slope of CO2 assimilation against intercellular CO2 pressures (A:Ci) at 36°C. Thus, a simultaneous increase in Rubisco and RCA contents leads to enhanced photosynthesis within the optimal temperature range.
在某些条件下，核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）限制了C3光合作用，因此是提高光合效率的一个潜在靶点。Rubisco的过量产生通常伴随着Rubisco活性的下降，并且在Rubisco过量产生的植物（RBCS-ox）中，Rubisco活化酶（RCA）与Rubisco的蛋白质比率（RCA/Rubisco）大幅降低。在此，我们培育了同时过量产生Rubisco和RCA的转基因水稻（Oryza sativa）植株（RBCS-RCA-ox）。RBCS-RCA-ox植株中的Rubisco含量增加了23%-44%，并且RCA/Rubisco水平与野生型植株相似或更高。然而，尽管RBCS-RCA-ox植株中Rubisco的活化状态得到了增强，但在25°C时，RBCS-RCA-ox植株的二氧化碳同化速率与野生型植株并无差异。另外，在适度高温（最佳范围为32°C-36°C）下，在等于或低于当前大气二氧化碳水平的条件下，RBCS-ox和RBCS-RCA-ox植株的二氧化碳同化速率高于野生型植株。RBCS-RCA-ox中Rubisco的活化状态仍高于RBCS-ox植株，并且在36°C时，RCA过量产生、RBCS-ox、RBCS-RCA-ox和野生型植株中活化的Rubisco含量与二氧化碳同化相对于细胞间二氧化碳压力的初始斜率（A:Ci）高度相关。因此，Rubisco和RCA含量的同时增加会在最佳温度范围内增强光合作用。
