Alternative splicing (AS)-derived TuPr-1-rk mRNA isoforms. a Structure of the 13 mRNA isoforms, named with Roman letters I-XIII with the wild-type full-length transcript designated as Isoform I. Asterisks indicate isoforms that are also found in hexaploid wheat (Lu et al. 2017). Open boxes and thick lines indicate exons and introns, respectively, and color shadings indicate regions encoding conserved domains as shown in Fig. 2. Vertical arrows indicate the positions of the early stop codon caused by alternative splicing (AS) as described in Table 2. Gray boxes denote the exons excluded due to the early stop. Numbers in superscript indicate the numbers of base pairs that are deleted (−) or added (+) to the native exons due to respective AS events. b Relative abundance of the 13 isoforms in the salt-treated G3135 plants as shown in Fig. 3. Percentage was calculated from a total of 150 cDNA clones obtained by reverse transcriptase (RT)-PCR using the same mRNA sample isolated at 48 h post treatment. PR-1 + TM + STKc, full-length protein; PR-1 + TM+(STKc), isoforms with an incomplete STKc domain; PR-1 ± TM, isoforms with PR-1 domain only (with or without the TM)