Analyses on the Infection Process of Rice Virus and the Spatiotemporal Expression Pattern of Host Defense Genes Based on a Determined-Part Inoculation Approach.

Tong Zhou,Shuhui Ma,Linlin Du,Feng Sun,Wei Guo,Jie Li,Chenyang Li,Yijun Zhou,Bo Zeng,Yunyue Wang,Ying Lan,Chengye Lu,Shuo Li,Zhaoyun Wang

doi:10.3390/pathogens11020144

Abstract

Rice viral diseases adversely affect crop yield and quality. Most rice viruses are transmitted through insect vectors. However, the traditional whole-plant inoculation method cannot control the initial inoculation site in rice plants because the insect feeding sites in plants are random. To solve this problem, we established a determined-part inoculation approach in this study that restricted the insect feeding sites to specific parts of the rice plant. Rice stripe virus (RSV) was used as the model virus and was inoculated at the bottom of the stem using our method. Quantitative real-time PCR and Western blot analyses detected RSV only present at the bottom of the Nipponbare (NPB) stem at 1 day post-inoculation (dpi), indicating that our method successfully controlled the inoculation site. With time, RSV gradually moved from the bottom of the stem to the leaf in NPB rice plants, indicating that systemic viral spread can also be monitored using this method. In addition, a cultivar resistant to RSV, Zhendao 88 (ZD88), was inoculated using this method. We found that RSV accumulation in ZD88 was significantly lower than in NPB. Additionally, the expression level of the resistant gene STV11 in ZD88 was highly induced at the initial invasion stage of RSV (1 dpi) at the inoculation site, whereas it remained relatively stable at non-inoculated sites. This finding indicated that STV11 directly responded to RSV invasion to inhibit virus accumulation at the invasion site. We also proved that this approach is suitable for other rice viruses, such as Rice black-streaked dwarf virus (RBSDV). Interestingly, we determined that systemic infection with RSV was faster than that with RBSDV in NPB, which was consistent with findings in field trails. In summary, this approach is suitable for characterizing the viral infection process in rice plants, comparing the local viral accumulation and spread among different cultivars, analyzing the spatiotemporal expression pattern of resistance-associated genes, and monitoring the infection rate for different viruses.

Highlights

Rice, a staple food consumed globally, is crucial for ensuring worldwide food security [1,2]
To verify whether the determined-part inoculation approach can control the initial invasion of the rice virus, the Nipponbare (NPB) was inoculated with Rice stripe virus (RSV) by using the determined-part inoculation method at the bottom of the stem (Figure 1) (SBPHs usually like to eat the stem in the field [27]) or by using the traditional whole-plant inoculation method [3,26]
The results showed that the accumulation of RSV-CP was only detected at the inoculation position 1 day after RSV inoculation at the bottom of the NPB stem (Figure 2B), whereas in plants inoculated by a whole-plant inoculation method, the accumulation of RSV-CP was detected in all parts of the plant (Supplemental Figure S1)

Summary

Introduction

A staple food consumed globally, is crucial for ensuring worldwide food security [1,2]. Rice virus disease seriously threatens the guarantee of the yield and quality of rice every year and causes huge economic losses. RSV belongs to the genus Tenuivirus and is transmitted by the insect vector small brown planthopper (Laodelphax striatellus, SBPH) [6,10,11,12,13]. SBPH can transmit Rice black-streaked dwarf virus (RBSDV), a member of the Fijivirus genus of the Reoviridae family [14]. RBSDV can infect gramineous crops, such as wheat, barley, oats, corn, and sorghum, causing serious economic loss by reducing crop productivity [4,15,16,17,18,19,20]

Methods

Results

Discussion

Conclusion