Three Cell Wall Degrading Enzymes and Sorghum Contribute to Virulence and Resistance in the Bacterial Leaf Streak Pathosystem.

With an increasing demand for renewable fuels, bioenergy crops are being developed with high sugar content and altered cell walls to improve processing efficiency. These traits may have unintended consequences for plant disease resistance. pv. (), the causal agent of sorghum bacterial leaf streak, is a wide-spread bacterial pathogen. Here, we show that expresses several bacterial cell wall degrading enzymes (CWDEs) during sorghum infection, and these are required for full virulence. In tolerant sorghum, infection results in induction of a key enzyme in monolignol biosynthesis, (), but this did not affect lignin content nor composition. Mutation of rendered the tolerant genotype susceptible. encodes caffeic acid -methyltransferase (COMT), an enzyme that generates sinapaldehyde as its major product. Growth inhibition of in the presence of sinapaldehyde was observed in vitro. We conclude that mutations that alter the components of the sorghum cell wall can reduce sorghum resistance to and that CWDEs contribute to bacterial virulence. Given the enhanced bioprocessing characteristics of sorghum, these results provide a cautionary tale for current and future efforts aimed at developing dedicated bioenergy crops.