Overexpression of Rubisco subunits with RAF1 increases Rubisco content in maize

First author: Coralie E. Salesse-Smith; Affiliations: Boyce Thompson Institute (博伊斯·汤姆森研究所): Ithaca, USA

Corresponding author: David B. Stern

Rubisco catalyses (催化) a rate-limiting step in photosynthesis and has long been a target for improvement due to its slow turnover rate (转化率). An alternative to modifying catalytic properties of Rubisco is to increase its abundance within C4 plant chloroplasts, which might increase activity and confer a higher carbon assimilation (碳同化) rate. Here, we overexpress the Rubisco large (LS) and small (SS) subunits with the Rubisco assembly chaperone (伴侣) RUBISCO ASSEMBLY FACTOR 1 (RAF1). While overexpression of LS and/or SS had no discernable (可辨别的) impact on Rubisco content, addition of RAF1 overexpression resulted in a  >30% increase in Rubisco content. Gas exchange (气体交换) showed a 15% increase in CO2 assimilation (ASAT) in UBI-LSSS-RAF1 transgenic plants, which correlated with increased fresh weight (鲜重) and in vitro Vcmax calculations. The divergence of Rubisco content and assimilation could be accounted for by the Rubisco activation state (活化状态), which decreased up to 23%, suggesting that Rubisco activase  (活化酶) may be limiting Vcmax, and impinging (冲击) on the realization (实现) of photosynthetic potential from increased Rubisco content.

Rubisco酶催化光合作用的一个限速反应，并由于其转化率较低，是长久以来提升植物光合的靶标。一个潜在的修饰Rubisco催化活性的方法就是提升其在C4植物中的含量，进而可能会增加Rubisco催化活性，提升碳同化速率。本文中，作者通过Rubisco组装分子伴侣RAF1过表达Rubisco的大、小亚基。过表达Rubisco的大、小亚基对于Rubisco含量并没有明显的影响，加上RAF1过表达的话会提升约30%的Rubisco含量。气体交换显示在UBI-LSSS-RAF1转基因株系中CO2同化增加了15%左右，且与鲜重和体外Vcmax的增加相关。Rubisco含量和同化的不一致可能是由于Rubisco的活化状态下降了23%所导致的，说明Rubisco活化酶可能会限制Vcmax，并且影响Rubisco含量提升后的潜在光合实现。

通讯：David B. Stern（https://btiscience.org/david-stern/）

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�研究方向：核基因如何调控叶绿体的基因及代谢活性。

doi: https://doi.org/10.1038/s41477-018-0252-4

Journal: Nature Plants

Published date: 01 October, 2018

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