Modulation of sugar and nitrogen in callus induction media alter PAL pathway, SA and biomass accumulation in rice callus

In this study, the effect of varying nitrogen and sucrose concentrations in culture media was evaluated with respect to biomass production, accumulation of flavonoids, anthocyanin, and associated gene expression in rice callus. The callus was induced on control MS (M1), sugar-deficient (M2), sugar-excessive (M3), nitrogen-deficient (M4), and nitrogen-excessive (M5) media. The results indicated that the callus induction percentage (CIP) as well as the size and fresh weight of the callus were inhibited by all types of media compared with control media. Varying the sucrose and nitrogen concentration significantly affected callus morphology and caused a browning effect. Genes related to flavonoid biosynthesis (CHS, CHI, F3H, FLS and DFR) were upregulated in the callus cultured in all four media types compared with control media. Likewise, flavonoid and anthocyanin accumulation were higher in callus grown in excessive sugar- and nitrogen-containing media compared with control media. Unlike flavonoids, salicylic acid (SA) regulation was significantly higher in callus grown in sugar- and nitrogen-deficient media compared with control media. Sugar content was significantly higher in callus cultured in sugar-excessive media, whereas it was reduced in the callus cultured in the other media types compared with control media. Finally, chlorophyll was reduced in all callus media compared with the control media.