FIGURE 2 Exon-intron structure and intron phases 0, 1, and 2 accounted for the proportion of all introns of AsA-GSH cycle enzyme genes and nitrogen metabolism enzyme genes in rice and similar genes in other species. (a) and (f), (b) and (g), (c) and (i), (d) and (h), (e) and (j) represent the exons and intron phases 0, 1, and 2, which accounted for the proportion of all introns in rice, Arabidopsis thaliana , Zea mays , Hordeum vulgare , and Sorghum bicolor , respectively. The blue rectangle represents the 5’-UTR and 3’-UTR, and the line represents introns; the unit of exon length is kb.
3.4| Effects of exogenous melatonin on the expression of enzymes involved in the AsA-GSH cycle and nitrogen metabolism in NaCl-stressed seedlings
As shown in (Figure 3a–d), NaCl treatment significantly decreased AsA, GSH, and ammonium nitrogen content and AAO, DHAR, GR, GPX, NR, GS, and GOGAT activities in seedlings, but significantly increased nitrate-nitrogen content. The results of exogenous melatonin at different concentrations (50–800 µmol ·L-1) opposed those of NaCl treatment. The heat maps of OsGR3 , OsGPX1 , OsNR2 , OsGS1 , andOsGOGAT1 represented by Log2 FC values among the different treatments were constructed (Figure 4a–b). Compared with control treatment, the color of OsGR3 , OsGPX1 ,OsNR2 , OsGS1 , and OsGOGAT1 on the heat map was green under NaCl stress, indicating that gene expression was significantly downregulated; the darker the green, the greater the degree of downregulation (Figure 4a–b). In other melatonin-pretreated samples, the color of the genes on the heat map was reddish, even red, indicating that the expression of the genes was upregulated; the darker the red, the higher the degree of upregulation (Figure 4a–b). Simultaneously, the expression levels of OsGR3 , OsGPX1 ,OsNR2 , OsGS1, and OsGOGAT1 in seedlings were detected by RT-qPCR. The results of gene expression were found to be similar to those on the heat map.