T6SS Accessory Proteins, Including DUF2169 Domain-Containing Protein and Pentapeptide Repeats Protein, Contribute to Bacterial Virulence in T6SS Group_5 of Burkholderia glumae BGR1.

Namgyu Kim,Hyejung Jung,Hyun-Hee Lee,Young-Su Seo,Jungwook Park,Gil Han

doi:10.3390/plants11010034

Namgyu Kim, Hyejung Jung + Show 4 more

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https://doi.org/10.3390/plants11010034

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Abstract

Burkholderia glumae are bacteria pathogenic to rice plants that cause a disease called bacterial panicle blight (BPB) in rice panicles. BPB, induced by B. glumae, causes enormous economic losses to the rice agricultural industry. B. glumae also causes bacterial disease in other crops because it has various virulence factors, such as toxins, proteases, lipases, extracellular polysaccharides, bacterial motility, and bacterial secretion systems. In particular, B. glumae BGR1 harbors type VI secretion system (T6SS) with functionally distinct roles: the prokaryotic targeting system and the eukaryotic targeting system. The functional activity of T6SS requires 13 core components and T6SS accessory proteins, such as adapters containing DUF2169, DUF4123, and DUF1795 domains. There are two genes, bglu_1g23320 and bglu_2g07420, encoding the DUF2169 domain-containing protein in the genome of B. glumae BGR1. bglu_2g07420 belongs to the gene cluster of T6SS group_5 in B. glumae BGR1, whereas bglu_1g23320 does not belong to any T6SS gene cluster in B. glumae BGR1. T6SS group_5 of B. glumae BGR1 is involved in bacterial virulence in rice plants. The DUF2169 domain-containing protein with a single domain can function by itself; however, Δu1g23320 showed no attenuated virulence in rice plants. In contrast, Δu2g07420DUF2169 and Δu2g07420PPR did exhibit attenuated virulence in rice plants. These results suggest that the pentapeptide repeats region of the C-terminal additional domain, as well as the DUF2169 domain, is required for complete functioning of the DUF2169 domain-containing protein encoded by bglu_2g07420. bglu_2g07410, which encodes the pentapeptide repeats protein, composed of only the pentapeptide repeats region, is located downstream of bglu_2g07420. Δu2g07410 also shows attenuated virulence in rice plants. This finding suggests that the pentapeptide repeats protein, encoded by bglu_2g07410, is involved in bacterial virulence. This study is the first report that the DUF2169 domain-containing protein and pentapeptide repeats protein are involved in bacterial virulence to the rice plants as T6SS accessory proteins, encoded in the gene cluster of the T6SS group_5.

Highlights

IntroductionB. glumae are bacteria pathogenic to rice plants, which cause a disease called bacterial panicle blight (BPB) in rice panicles [2,3]
Burkholderia glumae was first reported in Japan in the 1950s [1]
Our findings show that bglu_2g07420 and bglu_2g07410, belonging to the gene cluster of T6SS group_5 in B. glumae BGR1, encode the DUF2169 domain-containing protein and pentapeptide repeats protein, respectively, and contribute to the bacterial virulence to rice plants as the T6SS-associated proteins

Summary

Introduction

B. glumae are bacteria pathogenic to rice plants, which cause a disease called bacterial panicle blight (BPB) in rice panicles [2,3]. B. glumae has several virulence factors, such as toxins, proteases, lipases, extracellular polysaccharides, bacterial motility, and bacterial secretion systems [4,5,6,7,8,9,10]. B. glumae cause BPB in rice panicles, and bacterial wilt in rice stems and various other economically important crops, such as tomatoes, eggplants, hot peppers, and sesame [3,4]. The virulence factors of B. glumae contribute to its resistance against the host immune system and cause damage the host. T6SS group_1 of B. glumae BGR1 is involved in bacterial competition, whereas T6SS group_4 and group_5 contribute to bacterial virulence [3]

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