Analysis of express sequence tags from Arbuscular Mycorrhizal fungi (AMF) express during the pre-symbiotic stage of the fungus

Abstract

Arbuscular Mycorrhizal Fungi (AMF) are symbiotically associated with the roots of higher plants which enhance the overall nutritional status of plants. It is known that the overall growth and development of plants not only depend upon the performance of specific genotypes but their association is also affected by the various types of microbes. Therefore, the major aim of the study was the isolation and characterization of gene expression during the presymbiotic stage of AMF. In the present study, total RNA was extracted from spores of Rhizophagus irregularis grown under root organ culture (ROC). cDNA library was prepared and expressed sequence tag (EST) analysis was performed. Approximately 150 random clones were selected for EST sequencing analysis. Out of the 150 clones obtained, 1.5% carried inserts of the rRNA gene cluster. After excision, inserts from 72 randomly selected clones were sequenced. Database searches revealed that 74% of the clones had similarities to already known sequences. Putative genes for Ca2+-regulated symbiotic genes, cell cycle regulatory factors and precursors for lipid biosynthesis genes were discovered. A full-length mating gene was discovered using rapid amplification of cDNA ends (RACE). Studies revealed the presence of a putative mating type gene in mycorrhizal species that are evident in the sexual origin of AMF.