Enhancing plant photosynthesis through activating cells deficient in photosynthetic apparatus

Abstract

Much efforts have been devoted to identify options to improve plant photosynthetic capacity. Most of these engineering focuses more on enhancing photosynthetic capacity of the mesophyll cells. In this study, we specifically expressedCYTOKININRESPONSIVE GATA FACTOR 1 (CGA1)in the vascular bundle and bundle sheath cells (ProGLDPA: CGA1) which generally have low photosynthetic capacity. The introduction ofCGA1resulted in increased numbers and sizes of chloroplasts in both bundle sheath and vascular bundle, without noticeable difference in these properties in mesophylls. Additionally, compared with wild type (WT), transgenic lines showed enhanced development of mitochondria and peroxisomes. Leaf photosynthetic rates in these transgenic lines were higher than those in WT, especially under high light. Furthermore, the amount of RuBisCO, Vcmax, Jmax, and the number of starch granules were also significantly increased in the transgenic lines, which led to about 20% increase in biomass. Remarkably, the CO2compensation point ofProGLDPA: CGA1decreased compared with WT, resembling the characteristics of proto-Kranz during C4evolution. All these results indicated that enhancing photosynthetic properties of vascular bundle and bundle sheath cell is an effective approach to improve leaf photosynthesis, and highlighted that utilization of the cell lacking photosynthetic capacity is a promising way to improve plant photosynthesis for greater capacity.