Abstract
Xanthomonas oryzae pv. oryzicola (Xoc), the causal agent of bacterial leaf streak, is one of the most severe seed-borne bacterial diseases of rice. However, the molecular mechanisms underlying Xoc in response to oxidative stress are still unknown. In this study, we performed a time-course RNA-seq analysis on the Xoc in response to H2O2, aiming to reveal its oxidative response network. Overall, our RNA sequence analysis of Xoc revealed a significant global gene expression profile when it was exposed to H2O2. There were 7, 177, and 246 genes that were differentially regulated at the early, middle, and late stages after exposure, respectively. Three genes (xoc_1643, xoc_1946, xoc_3249) showing significantly different expression levels had proven relationships with oxidative stress response and pathogenesis. Moreover, a hypothetical protein (XOC_2868) showed significantly differential expression, and the xoc_2868 mutants clearly displayed a greater H2O2 sensitivity and decreased pathogenicity than those of the wild-type. Gene localization and phylogeny analysis strongly suggests that this gene may have been horizontally transferred from a Burkholderiaceae ancestor. Our study not only provides a first glance of Xoc's global response against oxidative stress, but also reveals the impact of horizontal gene transfer in the evolutionary history of Xoc.
Highlights
Xanthomonas consists of a large number of phytopathogenic bacteria that infect more than 400 host species, including a wide variety of economically important plants, such as rice, citrus, banana, cabbage, and bean [1, 2]
The sequencing depth in this experiment was more than 150 X, which is sufficient for further statistical analysis
The overall number of differentially expressed genes (DEGs) was similar to the number found in recent research related to human pathogens and environmental bacteria [24, 25], with the exception of differential expressed genes (DEGs) in the early state (7 min), which were almost 10 times smaller than in our study
Summary
Xanthomonas consists of a large number of phytopathogenic bacteria that infect more than 400 host species, including a wide variety of economically important plants, such as rice, citrus, banana, cabbage, and bean [1, 2]. The interaction complexity between Xoc and rice results from the outcome of a longstanding and ongoing evolutionary battle, in which the bacteria attempts to invade and multiply, while the rice plant’s cells attempt to recognize and defend against this invasion. Of these plant responses, oxidative burst is one of the initial response against pathogens [4].
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