Senescence-Specific Expression of RAmy1A Accelerates Non-structural Carbohydrate Remobilization and Grain Filling in Rice (Oryza sativa L.).

Ning Ouyang,Yanning Tan,Bingran Zhao,Citao Liu,Meijuan Duan,Zhizhong Sun,Xuewu Sun,Dong Yu,Lu Jin,Ling Liu,Dingyang Yuan,Hai Liu

doi:10.3389/fpls.2021.647574

Abstract

Remobilization of pre-anthesis NSCs (non-structural carbohydrates) is significant for effective grain filling in rice (Oryza sativa L.). However, abundant starch particles as an important component of NSCs are still present in the leaf sheath and stem at the late stage of grain filling. There are no studies on how bioengineering techniques can be used to improve the efficiency of NSC remobilization. In this study, RAmy1A was expressed under the senescence-specific promoter of SAG12, which was designed to degrade starch in the leaf sheath and stem during grain filling. RAmy1A mRNA successfully accumulated in the leaf, stem, and sheath of transgenic plants after anthesis. At the same time, the starch and total soluble sugar content in the leaf, stem, and leaf sheath were obviously decreased during the grain-filling period. The photosynthetic rate of transgenic lines was higher than that of the wild types by an average of 4.0 and 9.9%, at 5 and 10 days after flowering, respectively. In addition, the grain-filling rate of transgenic lines was faster than that of the wild types by an average of 26.09%. These results indicate an enhanced transport efficiency of NSCs from source tissues in transgenic rice. Transgenic rice also displayed accelerated leaf senescence, which was hypothesized to contribute to decreased grain weight.

Highlights

Grain filling is a significant and dynamic process for the final yield of rice
No significant increase in RAmy1A expression was observed in transgenic lines, compared with the wild types at the vegetative stage, while at the reproductive stage, the transcription level of RAmy1A in transgenic lines was strongly increased compared with the wild type, and the induction in the leaf tissue was 128 times greater at 21 DAF (Figure 1C)
This study was evaluated the effect of senescence stagespecific overexpression of RAmy1A on grain filling in rice

Summary

Introduction

Grain filling is a significant and dynamic process for the final yield of rice. Previous studies have shown that the assimilates required for grain filling are primarily supplied by leaf photosynthesis and non-structural carbohydrates (NSCs) reserved in leaf sheaths and stems before anthesis (Schnyder, 1993; Samonte et al, 2001; Xie et al, 2015; Zakari et al, 2020). NSCs can contribute to 10–40% of final grain yield, depending on the variety and environmental conditions (Takai et al, 2005; Yang and Zhang, 2010). NSCs reserved in the stems could enhance sink strength during grain filling and increase the filling efficiency (Yang and Zhang, 2010; Fu et al, 2011). A large amount of NSCs were not transported to the grains during the later filling period (Yang et al, 2002). Breeders can develop high-yielding rice varieties by improving the transport efficiency of reserved NSCs in leaf sheaths and stems (Takai et al, 2005)

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Discussion

Conclusion