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Endophytic fungus Serendipita indica belongs to the order Sebacinales. It is an extremely versatile root endophyte colonizing more than 150 different plant species including the model plant Arabidopsis thaliana. Colonization of S. indica triggers enhanced growth, early flowering, increase in seed content, alteration of secondary metabolite pathways and adaption to different biotic and abiotic stresses. This is why this fungus got ample attention by the plant researchers. In this study, we report modulation in expression of argininosuccinate synthase (AS), argininosuccinate lyase (AL) and arginase 2 (ARGAH2) genes in A. thaliana as a result of S. indica colonization. Similarly, expression of GUS reporter gene driven by AS and ARGAH2 promoters in roots was altered. AS, AL and ARGAH2 genes were down-regulated at early stage of root colonization i.e at 3 days post inoculation (dpi), with a subsequent up-regulation at later stages (7 and 14 dpi). Other arginine catabolism genes, Arginine decarboxylase-1 (ADC1), Arginine decarboxylase-2 (ADC2) and Pyrroline-5-carboxylate reductase (P5CR) were strongly up-regulated at later stages of S. indica colonization. Our findings show significant changes in expression of several important genes in arginine metabolic pathway upon S. indica colonization. These changes are very specific and strongly depend on the colonization phase of the fungus.
Keywords: AL; ARGAH1; ARGAH2; AS; Arginine metabolism; GUS; Quantitative RT-PCR; Serendipita indica