Li Bo, a professor at the National Key Laboratory of Agricultural Microbiology of Huazhong Agricultural University (HZAU) and the Hubei Hongshan Laboratory, recently published groundbreaking research in Nature Plants.

The study uncovered a molecular mechanism by which RuvC, a Holliday junction resolvase, regulates biofilm dynamics in Ralstonia solanacearum. This regulation promotes biofilm dissociation and bacterial spread. By utilizing newly identified functional genes, Li and his team developed a tomato variety with broad-spectrum resistance to R. solanacearum. This novel strategy was also successfully applied to improve the resistance of rice to bacterial blight.

Vascular bundle diseases pose one of the most significant threats to crops. These diseases interfere with water and nutrient transport, leading to plant wilting, death, and substantial economic losses.

Among these diseases, bacterial wilt caused by R. solanacearum stands out, as it has the potential to reduce the yield of Solanaceae like tomatoes by 30 to 50 percent annually, which in severe cases can exceed 70 percent. R. solanacearum infects over 250 plant species, presenting a major challenge to agricultural production.

In response to this problem, Li and his team conducted in-depth research on the biofilm formation mechanisms of R. solanacearum.

Biofilms, protective structures formed by bacteria, help them resist harsh environmental conditions and evade host immune responses. They play a critical role in bacterial spread and infection. The team identified the Holliday junction resolvase RuvC in the biofilm proteome of R. solanacearum, revealing a new mechanism by which RuvC enhances the diffusion and migration of the bacteria within the vascular bundles of tomatoes. This, in turn, positively regulates the pathogen's ability to cause disease.

Leveraging this discovery, the team developed a range of novel germplasm materials that offer broad-spectrum resistance to vascular bundle bacterial diseases in crops. These new materials significantly enhance crop resistance to bacterial wilt and bacterial blight by expressing secretory RuvC or its homologous proteins in the crops, according to their study.

For example, constitutive secretory RuvC in Solanaceae, such as tomatoes and tobacco improved survival rates by about 50 percent following infection by R. solanacearum. In rice, expressing a homologous RuvC protein from Xanthomonas oryzae also notably increased resistance to bacterial blight.

These findings not only reveal a new mechanism for biofilm regulation and bacterial diffusion of R. solanacearum in the xylem but also offer innovative strategies for improving crop disease resistance. By utilizing biofilm regulatory proteins derived from pathogens themselves, this approach avoids the environmental pollution and resistance risks associated with traditional chemical pesticides, while also enhancing crop resistance and yield stability.