Grafting as a Tool for Study of Phototropism in Phycomyces.

Physiological responses, such as phototropism and carotenogenesis, are usually exhibited through a specific cascade composed of several gene functions. The number of such gene functions can be determined by means of complementation analysis. For this purpose, a procedure is needed to produce heterokaryons easily and with a high success rate. Here, we present a method of grafting sporangiophores from different mutants to obtain heterokaryotic regenerates at the graft union, based on the large size of the sporangiophore and its remarkable regeneration capability.

Multiple genes for chitin synthase in the zygomycete fungus Phycomyces blakesleeanus.

Two different newly designed primer sets were used in PCR to amplify the fragments of chitin synthase (CHS) encoding genes (CHS) from the zygomycete fungus Phycomyces blakesleeanus, in which the cell wall is mainly made of chitin and chitosan, a deacetylated derivative from chitin. DNA sequencing and alignment analysis of the deduced amino acid sequences showed the possible existence of ten different genes. Six different DNA fragments, designated PbCHS1, PbCHS2, PbCHS3, PbCHS4, PbCHS5 and PbCHS6, homologous to chitin synthase genes were identified in 250-bp products. From 350-bp products, four different fragments, PbCHS7, PbCHS8, PbCHS9 and PbCHS10, were obtained. Clustal analysis suggested that while this fungus may not have class III-CHS, class I-, II- and IV-CHS could be present in multiple forms. Only PbCHS1, PbCHS2, PbCHS7 and PbCHS8 genes were actively expressed in the young germlings cultured in the liquid medium. Transcriptional products from PbCHS8 and PbCHS10, 8.2-kb long poly(A)(+)RNA, might suggest the existence of an unidentified type of CHS or the possibility of a multifunctional gene including CHS function.