Morphological and molecular differences in two strains of Ustilago esculenta

Ustilago esculenta is a fungal endophyte of Zizania latifolia that plays an important agricultural role in this vegetable crop. The purpose of this study was to characterize sporidial (T) and mycelial (M-T) strains of U. esculenta isolated from sporulating and non-sporulating galls on plants growing in Zhejiang province, China. Morphological comparisons of the T strain and M-T strain were made by optical and scanning electron microscope observation. Genetic differences were examined by sequencing the ITS region of the fungus and examining differential protein expression by two-dimensional gel electrophoresis and MALDI-TOF-MS/MS. The sporidial (T) and mycelial (M-T) strains differed in morphological characteristics of their in vitro single colony formations and in cell shape. Alignment of ITS sequences of the T strain and M-T strain revealed a single mutation between the T strain and M-T strain, but the sequences were the same within strains. A total of 146 proteins were only expressed in the M-T strain, and 242 proteins were only expressed in the T strain isolated from infected plants. A total of 222 proteins were up-regulated or down-regulated in the T strain when compared with the M-T strain. Of these, 18 proteins were identified and eight were associated with processes involving energy metabolism and the cytoskeleton. Two morphology-related proteins, MAP kinase kinase and actin, were differentially expressed. The differences noted in the T strain and M-T strain may lead to a better understanding of the life cycle and morphogenesis in U. esculenta.