Type Ⅲ secretion system 1 BPSS1395 gene promotes Burkholderia pseudomallei colonization and proliferation in tomato seedlings

Abstract

Objective To investigate the role of type Ⅲ secretion system 1 BPSS1395 gene of Burkholderia pseudomallei (B. pseudomallei) in promoting the infection of the bacterium in tomato seedlings. Methods Using Escherichia coli(E.coli) as the control, we infected the roots of tomato seedlings with wide-type strain B. pseudomallei BPC006 and detected the presence of the bacteria in the leaves of the plant with PCR. The localization of B. pseudomallei in tomato leaves was observed with transmission electron microscopy. At 3, 7, 10, 14, 17 and 21 d after the infection, the leaves of the tomato seedlings were randomly selected for detecting the intracellular survival of B. pseudomallei. We also compared the results of infections of the tomato seedlings with the wide-type B. pseudomallei strain BPC006, the ΔBPSS 1395 mutant strain and the BPSS1395-complemented strain by observing the pathological changes and PCR detection of bacterial colonization in the leaves on days 14 and 21 following the infection; the proliferation of each strain in the cells of the leaves was examined by counting the intracellular bacteria. Results A distinct BPSS1395 gene band could be amplified from the leaves of the tomato seedlings in B. pseudomallei infected group, while no E. coli-specific band was observed in the control group. Transmission electron microscopy revealed the presence of B. pseudomallei in the leaves after infection of the roots of the tomato seedlings, and the number of B. pseudomallei increased over time following the infection. Infection with ΔBPSS 1395 mutant resulted in no obvious pathologies in the leaves of the tomato seedlings, while the leaves of the seedlings infected with the wild-type strain BPC006 and BPSS1395-complemented strain were slightly wilted. Furthermore, no B. pseudomallei was detected in the leaves of the seedlings following infection with the ΔBPSS 1395 mutant; the BPSS1395-complemented strain and the wild-type strain showed similar proliferation ability in the leaf cells. Conclusion BPSS1395 gene can promote the colonization and proliferation of B. pseudomallei in tomato seedlings.

Keywords

• burkholderia pseudomallei
• bpss1395
• plant infection
• tomato seedling