Abstract Finding ways to increase Rubisco activity in crops to improve photosynthesis has long been a key objective. We have developed maize plants with transgenic overexpression of Rubisco subunits and Rubisco assembly factor 1 (RAF1) that resulted in higher Rubisco content, photosynthetic capacity and dry biomass under non-stressed growth conditions. The question remains, however, whether the transgenes conferring these effects could confer a growth penalty under stress conditions, given the nitrogen sink that Rubisco represents. In the present study, control and transgenic maize lines either overexpressing RAF1, both large and small subunits of Rubisco (LSSS), or all three (RAF1-LSSS), were subjected to mild, and severe drought conditions, and then re-watered. The results demonstrate that RAF1-LSSS, which has increased Rubisco abundance relative to the control, was slightly more affected than wild-type Rubisco level plants in terms of gas exchange and chlorophyll content after 14 days of stress. After returning plants to well-watered conditions, however, RAF1-LSSS displayed a more robust recovery compared to other genotypes. We attribute this to its high Rubisco content and the low malondialdehyde content noted prior to recovery, which indicates reduced oxidative degradation of lipids. Strong recovery was also observed in lines overexpressing RAF1 alone, in contrast with its lack of improved performance under non-stressed conditions. In contrast, LSSS displayed improved growth under non-stressed conditions, but showed a clear growth penalty during stress along with poor recovery. Taken together, our results suggest that while the high-Rubisco trait is neutral during water stress, recovery is more rapid once the stress is removed.

中文翻译：

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转基因过表达rubisco亚基和组装因子RAF1有利于玉米从干旱胁迫中恢复

摘要 寻找增加作物中 Rubisco 活性以改善光合作用的方法长期以来一直是一个关键目标。我们开发了具有转基因过表达 Rubisco 亚基和 Rubisco 组装因子 1 (RAF1) 的玉米植株，从而在非胁迫生长条件下产生更高的 Rubisco 含量、光合能力和干生物量。然而，问题仍然存在，考虑到 Rubisco 所代表的氮汇，赋予这些影响的转基因是否会在胁迫条件下赋予生长惩罚。在本研究中，过表达 RAF1、Rubisco 大亚基和小亚基 (LSSS) 或所有三个亚基 (RAF1-LSSS) 的对照和转基因玉米品系经受轻度和重度干旱条件，然后重新浇水。结果表明，RAF1-LSSS，与对照相比，Rubisco 丰度增加，在胁迫 14 天后，在气体交换和叶绿素含量方面比野生型 Rub​​isco 水平植物受到的影响略大。然而，在将植物恢复到充足的浇水条件后，与其他基因型相比，RAF1-LSSS 显示出更强劲的恢复。我们将此归因于其高 Rubisco 含量和回收前注意到的低丙二醛含量，这表明脂质的氧化降解减少。在单独过表达 RAF1 的品系中也观察到了强劲的恢复，与其在非压力条件下缺乏改善的性能相反。相比之下，LSSS 在非压力条件下显示出改善的生长，但在压力期间显示出明显的生长损失以及恢复不良。综合起来，