Two Different Transcripts of a LAMMER Kinase Gene Play Opposite Roles in Disease Resistance.

Alternative splicing of genes can increase protein diversity and affect mRNA stability. Genome-wide transcriptome sequencing has demonstrated that alternative splicing occurs in a large number of intron-containing genes of different species. However, despite the phenomenon having been known for decades, it is largely unknown how the alternatively spliced transcripts function differently. Here, we report that two alternatively spliced transcripts of the rice (Oryza sativa) LAMMER kinase gene OsDR11, long OsDR11L and short OsDR11S, play opposite roles in rice resistance against Xanthomonas oryzae pv oryzae (Xoo), which causes the most damaging bacterial disease in rice worldwide. Overexpressing OsDR11S or suppressing OsDR11L in rice enhanced resistance to Xoo, which was accompanied by an accumulation of jasmonic acid (JA) and induced expression of JA signaling genes. In contrast, suppressing OsDR11S was associated with increased susceptibility to Xoo, along with decreased levels of JA and expression of JA signaling genes. The OsDR11S and OsDR11L proteins colocalized in the nucleus. OsDR11L showed autophosphorylation activity in vitro, while OsDR11S did not. In the presence of OsDR11S, autophosphorylation of OsDR11L was inhibited, and overexpression of OsDR11S suppressed OsDR11L expression. OsDR11 appeared to contribute to a minor quantitative trait locus against Xoo These results suggest that OsDR11L is a negative regulator in rice disease resistance, which may be associated with suppression of JA signaling. The results also suggest that OsDR11S may inhibit the function of OsDR11L at both the transcription and protein kinase activity levels, leading to resistance against Xoo.