Preliminary Study On The Function Of Nitrogen Regulatory Gene AreA In Aspergillus Flavus

Aspergillus flavus,a saprophyte mostly found in the soil,is pathogenic to both animals and humans,causing diseases like aspergillosis and liver cancer.AreA is a global nitrogen regulatory gene,which belongs to the GATA transcription factors shown to be the major nitrogen regulatory gene,and areA is responsible for widely regulating the expression of genes involved in the catabolism of less favourable nitrogen sources in Aspergillus nidulans,in the absence of preferred nitrogen sources like glutamine and ammonium.Despite this,the function of the transcription factor AreA in A.flavus was not studied till now.In this study,we identified the major nitrogen regulatory gene,areA encoding an 866 aa protein,which is of significant identity to the areA of A.oryzae.The protein contained a signatory zinc finger domain,which is extremely conserved across diverse fungal species.The method of gene deletion and over-expression by homologous recombination was employed to elucidate the role of areA in A.flavus.The gene deletion strain(?areA)was unable to efficiently utilize secondary nitrogen sources for growth,conidiation and production of secondary metabolite,which showed that areA is important for the proper growth and development of A.flavus.It was also discovered that the ?areA strain had poorly developed conidiophores,when observed using complete media and hence,produced significantly less conidia than the wild-type.Aflatoxin(AFB1)production was also deteriorated in the ?areA strain,irrespective of the nitrogen source available.areA was seen to increase the sensitivity of A.flavus to genotoxic stress,as the growth of the wild-type strain was more inhibited than that of ?areA.However,?areA had a significantly increased susceptibility to osmotic,cell wall and oxidative stresses.areA deletion mutant could not effectively colonize hosts,maize and peanut seeds,as there was only an insignificant amount of conidia and aflatoxin production on the seeds.Hence,areA was found to be important in the pathogenicity of A.flavus.Finally,AreA was found to be localized in the nucleus in the presence of secondary nitrogen sources like alanine and proline,while it was localized in both cytoplasm and nucleus in the presence of glutamine and ammonium tartrate dibasic.This work sheds some light on the function of areA in nitrogen metabolism of A.flavus,and consequently aims at providing nouveau ways of controlling the animal and human pathogen,A.flavus.