Abstract：
As an important warm-season turfgrass species, bermudagrass (Cynodon dactylon L.) flourishes in warm areas around the world due to the existence of the C4 photosynthetic pathway. However, how C4 photosynthesis operates in bermudagrass leaves is still poorly understood. In this study, we performed single-cell RNA-sequencing on 5296 cells from bermudagrass leaf blades. Eight cell clusters corresponding to mesophyll, bundle sheath, epidermis and vascular bundle cells were successfully identified using known cell marker genes. Expression profiling indicated that genes encoding NADP-dependent malic enzymes (NADP-MEs) were highly expressed in bundle sheath cells, whereas NAD-ME genes were weakly expressed in all cell types, suggesting C4 photosynthesis of bermudagrass leaf blades might be NADP-ME type rather than NAD-ME type. The results also indicated that starch synthesis-related genes showed preferential expression in bundle sheath cells, whereas starch degradation-related genes were highly expressed in mesophyll cells, which agrees with the observed accumulation of starch-filled chloroplasts in bundle sheath cells. Gene co-expression analysis further revealed that different families of transcription factors were co-expressed with multiple C4 photosynthesis-related genes, suggesting a complex transcription regulatory network of C4 photosynthesis might exist in bermudagrass leaf blades. These findings collectively provided new insights into the cell-specific expression patterns and transcriptional regulation of photosynthetic genes in bermudagrass.
摘要：
作为一种重要的暖季型草坪草，由于C4光合途径的存在，百慕大草（CynodondactylonL.）在世界各地的温暖地区蓬勃发展。然而,百慕大草叶片中C4光合作用的运作方式仍然知之甚少。在这项研究中,我们对百慕大草叶片的5296个细胞进行了单细胞RNA测序。对应于叶肉的八个细胞簇，束鞘,使用已知的细胞标记基因成功鉴定了表皮和维管束细胞。表达谱分析表明，编码NADP依赖性苹果酸酶（NADP-ME）的基因在束鞘细胞中高表达，而NAD-ME基因在所有细胞类型中均弱表达，表明百慕大草叶片的C4光合作用可能是NADP-ME型而不是NAD-ME型。结果还表明，淀粉合成相关基因在束鞘细胞中表现出优先表达，而淀粉降解相关基因在叶肉细胞中高表达，这与在束鞘细胞中观察到的淀粉填充叶绿体的积累一致。基因共表达分析进一步揭示了不同家族的转录因子与多个C4光合作用相关基因共表达,表明百慕大草叶片中可能存在C4光合作用的复杂转录调控网络。这些发现共同为百慕大草中光合基因的细胞特异性表达模式和转录调控提供了新的见解。
