Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK.
Plant J. 2020 Jul;103(2):742-751. doi: 10.1111/tpj.14766. Epub 2020 May 4.
The regulation of Rubisco, the gatekeeper of carbon fixation into the biosphere, by its molecular chaperone Rubisco activase (Rca) is essential for photosynthesis and plant growth. Using energy from ATP hydrolysis, Rca promotes the release of inhibitors and restores catalytic competence to Rubisco-active sites. Rca is sensitive to moderate heat stress, however, and becomes progressively inhibited as the temperature increases above the optimum for photosynthesis. Here, we identify a single amino acid substitution (M159I) that fundamentally alters the thermal and regulatory properties of Rca in bread wheat (Triticum aestivum L.). Using site-directed mutagenesis, we demonstrate that the M159I substitution extends the temperature optimum of the most abundant Rca isoform by 5°C in vitro, while maintaining the efficiency of Rubisco activation by Rca. The results suggest that this single amino acid substitution acts as a thermal and regulatory switch in wheat Rca that can be exploited to improve the climate resilience and efficiency of carbon assimilation of this cereal crop as temperatures become warmer and more volatile.
Rubisco 是碳固定进入生物圈的关键酶，其分子伴侣 Rubisco 激活酶（Rca）对光合作用和植物生长至关重要。Rca 利用 ATP 水解产生的能量，促进抑制剂的释放，并恢复 Rubisco 活性位点的催化能力。然而，Rca 对中等热应激敏感，随着温度超过光合作用的最适温度，其活性逐渐受到抑制。在这里，我们鉴定了一个单一的氨基酸取代（M159I），它从根本上改变了面包小麦（Triticum aestivum L.）中 Rca 的热和调节特性。通过定点突变，我们证明该 M159I 取代使最丰富的 Rca 同工型的体外最适温度提高了 5°C，同时保持了 Rca 对 Rubisco 的激活效率。结果表明，这种单一的氨基酸取代在小麦 Rca 中充当了热和调节开关，可用于提高这种谷物作物的气候适应能力和碳同化效率，因为温度变得更加温暖和多变。
