PSARK::IPT expression causes protection of photosynthesis in tobacco plants during N deficiency

• N-deficiency affects primary photosynthesis and sugar metabolism.
• Transgenic plants expressing IPT gene coding the rate-limiting step in CKs synthesis.
• WT plants under N-limited, reduced biomass and photosynthetic parameters.
• Transgenic plants under N-limited, maintained biomass and photosynthetic parameters.
• Expression of PSARK::IPT in tobacco improves the strength of the sink under N-limited.

Wild type (WT) and transgenic tobacco plants expressing isopentenyltransferase (IPT), a gene coding the rate-limiting step in cytokinins (CKs) synthesis, were grown under limited nitrogen (N) conditions. WT tobacco plants under N deficit showed a drastic reduction in photosynthetic rate (A) and the maximum carboxylation rate of Rubisco (Vcmax), the maximum rate of the electron transport (Jmax) and the use of triose-P (TPU) parameters. However, the expression an IPT gene driven by PSARK, a stress-and maturation-induced promoter, in tobacco plants under N deficiency leads the maintenance of photosynthesis and leaf biomass related with the maintenance of sm-Rubisco transcripts levels. Limited increase in sugar concentration as well as the maintenance of leaf biomass observed in transgenic plants would indicate CKs may play a role in the sink limitation caused by deficiency of N, enhancing the strength of the sink, such as young leaves, and enhancing foliar biomass under severe N deficiency.