2.3. RNA isolation
Total RNA was isolated from boll of uninfected and A. flavus infected cotton using Spectrum total RNA isolation kit (Sigmae Aldrich, St. Louis, MO) at different time points after infection. The RNA was independently extracted from cottonseed and pericarp from each infected locules (L1) and three adjacent/distal locules (Adj), respectively. Total RNA was quantified by an ND-1000 spectrophotometer (Nanodrop Technologies, Wilmington, DE). The RNA integritywas also assessed by running 2 ml of total RNA in a 1.2% (w/v) agarose/formaldehyde gel, stained with ethidium bromide, and visualized under UV light. An aliquot of 1 mg RNA extracted from adjacent/distal locules (Adj) of cottonseed or pericarp was pooled for cDNA preparation.