英国剑桥大学Julian M. Hibberd，Leonie H. Luginbuehl和美国索尔克生物研究所Joseph R. Ecker共同合作，近期取得重要工作进展。他们研究发现，祖先细胞身份网络的功能外适应促成了C₄光合作用的形成。相关研究成果2024年11月20日在线发表于《自然》杂志上。

据介绍，C₄光合作用被地球上产量最高的植物所利用，与祖先的C₃途径相比，它的效率提高了50%。在60多个C₄谱系中，CO₂固定在组织之间进行划分，束鞘细胞被光合作用激活。束鞘如何获得这种允许高效光合作用的替代身份尚不清楚。

研究人员表明，C₄叶片中束鞘基因表达的变化与C₃叶片中发现的预先存在的顺式编码的增加有关。从单核基因表达和染色质可及性图谱中，研究人员发现了DNA与单指（DOF）基序的结合，这些基序定义了主要作物C₃水稻和C₄高粱的束鞘身份。在C₄高粱束鞘细胞中重新连接以强烈表达的光合作用基因，获得了DOF识别的顺式元件。

这一发现与一个简单的模型一致，在该模型中，C₄光合作用基于与束鞘身份相关的祖先顺式密码的补充。这些元素的获得利用了C₃和C₄叶片中细胞类型之间转录因子的稳定模式，以激活束鞘中的光合作用。

总之，这一研究成果为复杂C₄途径的演化提供了分子见解，也可能指导C₃作物C₄光合作用的合理工程，以提高作物的生产力和抗逆性。

附：英文原文

Title: Exaptation of ancestral cell-identity networks enables C4 photosynthesis

Author: Swift, Joseph, Luginbuehl, Leonie H., Hua, Lei, Schreier, Tina B., Donald, Ruth M., Stanley, Susan, Wang, Na, Lee, Travis A., Nery, Joseph R., Ecker, Joseph R., Hibberd, Julian M.

Issue&Volume: 2024-11-20

Abstract: C4 photosynthesis is used by the most productive plants on the planet, and compared with the ancestral C3 pathway, it confers a 50% increase in efficiency1. In more than 60 C4 lineages, CO2 fixation is compartmentalized between tissues, and bundle-sheath cells become photosynthetically activated2. How the bundle sheath acquires this alternate identity that allows efficient photosynthesis is unclear. Here we show that changes to bundle-sheath gene expression in C4 leaves are associated with the gain of a pre-existing cis-code found in the C3 leaf. From single-nucleus gene-expression and chromatin-accessibility atlases, we uncover DNA binding with one finger (DOF) motifs that define bundle-sheath identity in the major crops C3 rice and C4 sorghum. Photosynthesis genes that are rewired to be strongly expressed in the bundle-sheath cells of C4 sorghum acquire cis-elements that are recognized by DOFs. Our findings are consistent with a simple model in which C4 photosynthesis is based on the recruitment of an ancestral cis-code associated with bundle-sheath identity. Gain of such elements harnessed a stable patterning of transcription factors between cell types that are found in both C3 and C4 leaves to activate photosynthesis in the bundle sheath. Our findings provide molecular insights into the evolution of the complex C4 pathway, and might also guide the rational engineering of C4 photosynthesis in C3 crops to improve crop productivity and resilience3,4.

DOI: 10.1038/s41586-024-08204-3

Source: https://www.nature.com/articles/s41586-024-08204-3