Formation of Proto-Kranz in C3 Rice Induced by Spike-Stalk Injection Method.

Dexing Jiang,Wenwen Gao,Haizi Zhang,Feng Wang,Guoxiang Chen,Chuangen Lv,Xi Tong

doi:10.3390/ijms22094305

Abstract

Introduction of C4 photosynthetic traits into C3 crops is an important strategy for improving photosynthetic capacity and productivity. Here, we report the research results of a variant line of sorghum–rice (SR) plant with big panicle and high spikelet density by introducing sorghum genome DNA into rice by spike-stalk injection. The whole-genome resequencing showed that a few sorghum genes could be integrated into the rice genome. Gene expression was confirmed for two C4 photosynthetic enzymes containing pyruvate, orthophosphate dikinase and phosphoenolpyruvate carboxykinase. Exogenous sorghum DNA integration induced a series of key traits associated with the C4 pathway called “proto-Kranz” anatomy, including leaf thickness, bundle sheath number and size, and chloroplast size in bundle sheath cells. Significantly, transgenic plants exhibited enhanced photosynthetic capacity resulting from both photosynthetic CO2-concentrating effect and improved energy balance, which led to an increase in carbohydrate levels and productivity. Furthermore, such rice plant exhibited delayed leaf senescence. In summary, this study provides a proof for the feasibility of inducing the transition from C3 leaf anatomy to proto-Kranz by spike-stalk injection to achieve efficient photosynthesis and increase productivity.

Highlights

Introduction ofC4 photosynthetic traits into C3 crops is an important strategy for improving photosynthetic capacity and productivity
The clean data were aligned to the high-quality indica rice R498 genome and sorghum BTx623 genome using the Burrows–Wheeler Aligner (BWA)
158,047,250 and 174,529 high-quality reads were generated from the indica rice R498 genome and sorghum BTx623 genome, respectively, among which 149,439,894 (94.55%) and 124,282 (71.21%) reads were uniquely and confidently mapped to the reference genome, indicating that a small number of sorghum genes can be integrated into the rice genome by spike-stalk injection (Table S1, Figure 1A)

Summary

Introduction

Introduction ofC4 photosynthetic traits into C3 crops is an important strategy for improving photosynthetic capacity and productivity. Exogenous sorghum DNA integration induced a series of key traits associated with the C4 pathway called “proto-Kranz” anatomy, including leaf thickness, bundle sheath number and size, and chloroplast size in bundle sheath cells. Transgenic plants exhibited enhanced photosynthetic capacity resulting from both photosynthetic CO2 -concentrating effect and improved energy balance, which led to an increase in carbohydrate levels and productivity. Such rice plant exhibited delayed leaf senescence. This study provides a proof for the feasibility of inducing the transition from C3 leaf anatomy to proto-Kranz by spike-stalk injection to achieve efficient photosynthesis and increase productivity. In comparison with the ancestral C3 pathway, C4 plants form a special carbon shuttle system called

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