Abstract: The full-length cDNA sequence of the MLO gene was cloned via RACE-PCR from
muskmelon（Cucumis melo L.），and was designated as CmMLO2（GenBank Accession No. FJ713542）.
The gene is 1 713 bp long and encodes a 570-amino acid peptide with a seven-transmembrane domain
topology，and is a typical transmembrane protein. Its expression pattern was analyzed using quantitative
real-time PCR after the melon leaf was infected with powdery mildew. The results indicate that CmMLO2
is mainly expressed in melon leaves in a tissue-specific distribution. Moreover，CmMLO2 may play a
crucial role in the pathogenesis of powdery mildew. After the efficient of dsRNA constructs were
examined via pFGC1008-CmMLO2 were introduced into Agrobacterium tumefaciens and transformed into
melon wild type with the methods of Agrobacterium-mediated leaf disc transformation. The material of
broad-spectrum powdery mildew resistance against P. xanthii in muskmelon was obtained by
ihpRNAi-mediated knock-down of CmMLO2.

Key words: melon, powdery mildew, MLO, gene expression, genetic transformation