Figure 5. Sheath-to-blade Na⁺ transfer control in rice upon salt stress.

(A) Total OsHKT1;4 transcript level measured by qRT-PCR (+SEM; n = 3 to 4 replicates per sheath; three technical replicates per biological sample) in individual leaf sheath of Pokkali (Po) and Nipponbare (Ni). Three leaf sheaths were assessed, S2 to S4, from the oldest one to the youngest. (B) HPLC quantification of functional OsHKT1;4 transcripts and non-functional spliced variants SV1 and SV2 (+/− SEM; n = 3 to 4 replicates per sheath) in individual leaf sheath of Po and Ni, as a percentage of the total amount of transcripts reported in panel A. Leafs 2 and 3 were fully mature whereas leaf 4, although bigger than leaf 3, was still expending. (C) Correlation between functional OsHKT1;4 expression levels in individual sheath (Total OsHKT1;4 transcript level from panel A multiplied by the percentage of functional OsHKT1;4 transcript from panel B; +/− SEM; n = 3 to 4 replicates per sheath) and Na⁺ concentrations in the corresponding blades, measured by flame photometry (+/− SEM; n = 5) in three independent leaves (L2 to L4, from the oldest to the youngest) in Po and Ni.