Transcriptome analysis of xa5-mediated resistance to bacterial leaf streak in rice (Oryza sativa L.)

Xiaofang Xie,Binghui Zhang,Yan Zheng,Huazhong Guan,Jing Zhang,Tao Lan,Weiren Wu,Mingyue Qin,Zhiwei Chen

doi:10.1038/s41598-020-74515-w

Xiaofang Xie, Binghui Zhang + Show 7 more

Open Access

https://doi.org/10.1038/s41598-020-74515-w

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Abstract

Bacterial leaf steak (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a devastating disease in rice production. The resistance to BLS in rice is a quantitatively inherited trait, of which the molecular mechanism is still unclear. It has been proved that xa5, a recessive bacterial blast resistance gene, is the most possible candidate gene of the QTL qBlsr5a for BLS resistance. To study the molecular mechanism of xa5 function in BLS resistance, we created transgenic lines with RNAi of Xa5 (LOC_Os05g01710) and used RNA-seq to analyze the transcriptomes of a Xa5-RNAi line and the wild-type line at 9 h after inoculation with Xoc, with the mock inoculation as control. We found that Xa5-RNAi could (1) increase the resistance to BLS as expected from xa5; (2) alter (mainly up-regulate) the expression of hundreds of genes, most of which were related to disease resistance; and (3) greatly enhance the response of thousands of genes to Xoc infection, especially of the genes involved in cell death pathways. The results suggest that xa5 is the cause of BLS-resistance of QTL qBlsr5a and it displays BLS resistance effect probably mainly because of the enhanced response of the cell death-related genes to Xoc infection.

Highlights

Bacterial leaf streak (BLS) is a disease caused by the gram-negative bacterial pathogen Xanthomonas oryzae pv. oryzicola (Xoc) in rice
(NIP and Minghui 86 (MH86)) and RNA interference (RNAi) lines with Bacterial leaf steak (BLS) lesions at 15 days after Xoc inoculation, N and M represent RNAi lines derived from Nipponbare and MH86, respectively. (B) Lesion lengths of WT and T 2 RNAi lines measured at 15 days after Xoc inoculation. (C) Relative expression levels of Xa5 in WT and T 2 RNAi lines at 15 days after Xoc inoculation
We revealed that Xa5-RNAi could greatly alter the expression of many genes related to disease resistance and enhance transcriptional response to Xoc, and Xa5 affects BLS resistance probably mainly by regulating the expression of genes involved in cell death

Summary

Introduction

Bacterial leaf streak (BLS) is a disease caused by the gram-negative bacterial pathogen Xanthomonas oryzae pv. oryzicola (Xoc) in rice. Oryzae (Xoo)[22,23], implying that suppression of the dominant allele of LOC_Os05g01710 (Xa5) from the susceptible parent would increase the BLS resistance if it is really the gene responsible for the qBlsr5a effect. This implication has been verified by the result of RNA interference (RNAi) of Xa521,24, in which the Xa5-RNAi lines display enhanced resistance to BLS with little influence on agronomic traits (only slightly reducing plant height)[24]. It is rational to infer that xa[5] is the cause of the BLS-resistance effect of qBlsr5a, the possibility of contribution from the other two genes in the interval cannot be completely excluded

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