Wall composition of the protoplastic Entomophthorales

Use of cell culture media for cultivation of the mite pathogenic fungi Neozygites tanajoae and Neozygites floridana

The pathogenic fungus Neozygites tanajoae, one of the most efficient natural enemies of the cassava green mite (CGM) Mononychellus tanajoa in Brazil, was introduced experimentally in Benin in 1998/1999 for the control of CGM. Isolation methods and culture media for in vitro production of N. tanajoae are reported for the first time in this study. Continuous growth of N. tanajoae was achieved using medium NT-1 (IPL-41+5-10% fetal bovine serum+0.3% lactalbumin hydrolysate+0.3% yeastolate). This medium supported production of N. tanajoae up to 1.53 (+ or - 0.08) x 10(7) hyphal bodies/mL after 8 days. The growth of N. tanajoae from Cruz das Almas, Brazil, was compared to the growth of two Neozygites floridana isolates with wider host ranges from North Carolina, US, and Palmira, Colombia, in 11 cell culture media. We demonstrated that differences in nutritional requirements exist between N. tanajoae and the similar species, N. floridana. N. tanajoae is a particularly fastidious species highly specific to CGM and grows well in few media while N. floridana which is less host specific, grows in a broader range of media, including serum free media. N. floridana isolates produced more than 2 x 10(6) hyphal bodies/mL in > or =7 of the 11 media tested. However, the N. tanajoae isolate reached the same final concentration in only 3 media. Cell densities of N. tanajoae also increased slower than in N. floridana isolates in most media. N. tanajoae differed morphologically from the two N. floridana isolates in vitro. Hyphal bodies of eight N. tanajoae isolates are shorter than hyphal bodies of the two N. floridana isolates. The distinction of these two species was initially proposed based on host specificity, genetic and physiological patterns and is supported by the results presented in this study.

Cloning of two chitin synthase gene fragments from a protoplastic entomophthorale

Chitin synthase expression was studied in spontaneously produced protoplasts and in hyphal bodies of the Entomophthorale species Entomophaga aulicae. The absence of wall in protoplasts was correlated to an absence of chitin synthase. Two chitin synthase activities with different biochemical characteristics have been detected in the hyphal bodies. Two chitin synthase gene fragments EaCHS1 and EaCHS2 of 600 bp were obtained using PCR amplification of genomic DNA. Their amino acid sequences showed 75% identity. Compared with other fungal chitin synthases, they belong to class II. EaCHS1 and EaCHS2 were used to probe total RNA from E. aulicae hyphal bodies and protoplasts. A single transcript of 2.4 kb hybridized only with EaCHS1 in protoplasts and hyphal bodies.