Improved bacterial leaf blight disease resistance in the major elite Vietnamese rice cultivar TBR225 via editing of the OsSWEET14 promoter.

Phuong Nguyen Duy,Ngoc Phuong Pham,Florence Auguy,Dai Tran Lan,Huong Bui Thi Thu,Tran Bao Manh,Xuan Hoi Pham,Ha Nguyen Thanh,Hang Pham Thu,Huong Phung Thi Thu,Sebastien Cunnac

doi:10.1371/journal.pone.0255470

Abstract

TBR225 is one of the most popular commercial rice varieties in Northern Vietnam. However, this variety is highly susceptible to bacterial leaf blight (BLB), a disease caused by Xanthomonas oryzae pv. oryzae (Xoo) which can lead to important yield losses. OsSWEET14 belongs to the SWEET gene family that encodes sugar transporters. Together with other Clade III members, it behaves as a susceptibility (S) gene whose induction by Asian Xoo Transcription-Activator-Like Effectors (TALEs) is absolutely necessary for disease. In this study, we sought to introduce BLB resistance in the TBR225 elite variety. First, two Vietnamese Xoo strains were shown to up-regulate OsSWEET14 upon TBR225 infection. To investigate if this induction is connected with disease susceptibility, nine TBR225 mutant lines with mutations in the AvrXa7, PthXo3 or TalF TALEs DNA target sequences of the OsSWEET14 promoter were obtained using the CRISPR/Cas9 editing system. Genotyping analysis of T0 and T1 individuals showed that mutations were stably inherited. None of the examined agronomic traits of three transgene-free T2 edited lines were significantly different from those of wild-type TBR225. Importantly, one of these T2 lines, harboring the largest homozygous 6-bp deletion, displayed decreased OsSWEET14 expression as well as a significantly reduced susceptibility to a Vietnamese Xoo strains and complete resistance to another one. Our findings indicate that CRISPR/Cas9 editing conferred an improved BLB resistance to a Vietnamese commercial elite rice variety.

Highlights

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major bacterial disease that causes 10%-20% annual reduction in rice production worldwide [1]
OsSWEET14/Os11N3 was previously identified as a susceptibility gene for Xoo strains relying on either of the AvrXa7, PthXo3, TalF or TalC transcription activatorlike effectors (TALEs) for infection of the rice cultivars Nipponbare and Kitaake [11]
Because Xoo strains tend to frequently target this gene, we first sequenced a region of the OsSWEET14 promoter from rice cultivar TBR225 to examine if it carries documented target Effector-Binding Elements (EBEs)

Summary

Introduction

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a major bacterial disease that causes 10%-20% annual reduction in rice production worldwide [1]. Oryzae (Xoo) is a major bacterial disease that causes 10%-20% annual reduction in rice production worldwide [1]. The virulence of Xoo depends on the transcriptional activation of specific host disease-susceptibility (S) genes by a subgroup of bacterial type III effectors, called transcription activatorlike effectors (TALEs) [2]. DNA binding involves recognition principles that have been largely deciphered and applied to the computational prediction of TALEs target DNA sequences [3,4]. This and earlier work has fostered the identification of TALEs transcriptional targets in the rice genome and of rice BLB S genes [2]

Methods

Results

Conclusion