3.5 N transporters and glutamate receptors were differentially altered in the leaf and SAM

Since the N distribution showed dramatic change, we specifically screened for the N metabolism-related gene expression in the transcriptome profile. Of the 210 N-related genes, 164 had expression (FPKM>0.1). Among them, 158 genes were significantly impacted by the tissue type, 109 genes were affected by N application rate, and 94 were altered by [CO2] (Table S2). Apparently, eCO2 exerted a less influential effect to this specific category of genes than the N application. Further ascribing the putative functions of those being significantly affected by [CO2] had revealed that 20 of the 94 (21.3%) were glutamate receptors and nitrate or ammonium transporters. In contrast, only seven of 70 (10%) CO2 non-responsive genes belonged to these groups. It seems that more N metabolite receptors and transporters were specifically altered by eCO2, suggesting that N redistribution/reallocation may become more active under the eCO2. Among them, nine genes displayed contrasting induction and suppression changes between the leaf and SAM (Fig. 5). They were putative major facilitator family transporter (NRT2.3a/b, LOC_Os01g50820, Fig. 5A), ammonium transporters (LOC_Os01g61510, LOC_Os02g34580, and LOC_Os03g62200, Fig. 5B-D), high affinity nitrate transporter (LOC_Os04g40410, Fig. 5E) and peptide transporter PTR2 (NRT1.1a/b, LOC_Os10g40600, Fig. 5F). The others were all putative glutamate receptors (LOC_Os06g08910, LOC_Os09g26144, and LOC_Os09g26160, Fig. 5G-H). These genes were likely the critical contributor to the change of N distribution among organs in the eCO2 adaptation process in rice plant.