Mining Cytochrome b561 proteins from plant genomes

Cytochrome b561 (Cyt-b561) proteins are important for plant growth, development, and prevention of damage to plants. Because of their high sequence divergence, thorough mining of Cyt-b561 proteins from plant genomes are not easy. Currently there is only one Cyt-b561 gene found in the maize and none in the soybean genome. However, 22 have been identified in the Arabidopsis thaliana genome. We tested alignment-free protein classifiers based on partial least squares (PLS) and support vector machines to identify Cyt-b561. These classifiers performed better than profile hidden Markov models and PSI-BLAST. Using these classifiers we identified new Cyt-b561-related proteins from four plant genomes.