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<i>Ustilago esculenta</i> is a smut fungus that obligately infects <i>Zizania latifolia</i> and stimulates tissue swelling to form galls. Unlike T-type, MT-type <i>U. esculenta</i> can only proliferate within plant tissues and infect the offspring of their host. Production of telispores, haploid life, and plant cuticle penetration are not essential for it, which may lead to the degeneration in these processes. Transcriptome changes during the mating of T- and MT-type <i>U. esculenta</i> were studied. The functions of several secreted proteins were further confirmed by knock-out mutants. Our results showed that MT-type <i>U. esculenta</i> can receive environmental signals in mating and circumstance sensing as T-type does. However, MT-type <i>U. esculenta</i> takes a longer time for conjunction tube formation and cytoplasmic fusion. A large number of genes encoding secreted proteins are enriched in the purple co-expression module. They are significantly up-regulated in the late stage of mating in T-type <i>U. esculenta</i>, indicating their relationship with infecting. The knock-out of <i>g6161</i> (xylanase) resulted in an attenuated symptom. The knock-out of <i>g943</i> or <i>g4344</i> (function unidentified) completely blocked the infection at an early stage. This study provides a comprehensive comparison between T- and MT-type during mating and identifies two candidate effectors for further study.