Rubisco activase (Rca) facilitates the release of sugar‐phosphate inhibitors from the active sites of Rubisco and thereby plays a central role in initiating and sustaining Rubisco activation. In Arabidopsis, alternative splicing of a single Rca gene results in two Rca isoforms, Rca‐α and Rca‐β. Redox modulation of Rca‐α regulates the function of Rca‐α and Rca‐β acting together to control Rubisco activation. Although Arabidopsis Rca‐α alone less effectively activates Rubisco in vitro, it is not known how CO₂ assimilation and plant growth are impacted. Here, we show that two independent transgenic Arabidopsis lines expressing Rca‐α in the absence of Rca‐β (‘Rca‐α only’ lines) grew more slowly in various light conditions, especially under low light or fluctuating light intensity, and in a short day photoperiod compared to wildtype. Photosynthetic induction was slower in the Rca‐α only lines, and they maintained a lower rate of CO₂ assimilation during both photoperiod types. Our findings suggest Rca oligomers composed of Rca‐α only are less effective in initiating and sustaining the activation of Rubisco than when Rca‐β is also present. Currently there are no examples of any plant species that naturally express Rca‐α only but numerous examples of species expressing Rca‐β only. That Rca‐α exists in most plant species, including many C3 and C4 food and bioenergy crops, implies its presence is adaptive under some circumstances.

中文翻译：

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仅表达氧化还原调节的Rca-α同工型的拟南芥植物已经限制了光合作用和植物生长。

Rubisco激活酶（Rca）有助于从Rubisco的活性部位释放糖磷酸酯抑制剂，因此在启动和维持Rubisco激活中起着核心作用。在拟南芥中，单个Rca基因的可变剪接产生两个Rca亚型，Rca-α和Rca-β。Rca-α的氧化还原调节调节Rca-α和Rca-β共同起作用以控制Rubisco活化的功能。尽管仅拟南芥Rca-α在体外激活Rubisco的效果较差，但尚不知道CO ₂如何同化和植物生长受到影响。在这里，我们显示了在不存在Rca-β的情况下，两个表达Rca-α的独立转基因拟南芥品系（“仅Rca-α”品系）在各种光照条件下（尤其是在弱光或光照强度变化的情况下）以及在与野生型相比，短日照期更短。仅Rca-α系的光合诱导较慢，并且它们维持较低的CO ₂速率在两种光周期类型下均化。我们的研究结果表明，仅由Rca-α组成的Rca低聚物在引发和维持Rubisco活化方面效果不如也存在Rca-β。目前，没有任何植物物种仅自然表达Rca-α的例子，但是有许多仅表达Rca-β的物种的例子。Rca-α存在于大多数植物物种中，包括许多C3和C4食品和生物能源作物，这表明它的存在在某些情况下具有适应性。