SALT-INDUCED SYSTEMIC CA2+SIGNAL REGULATES PRE-mRNA SPLICING IN ARABIDOPSIS THALIANA

Plants adjust their biological processes to cope with numerous environmental factors. Alternative pre-mRNA splicing is a common post-transcriptional regulatory mechanism of environmental stress tolerance, such as in response to high salt exposure. Salinity induces transcriptome-wide reprograming via regulation of pre-mRNA splicing; however, the early response signals that trigger this modification are currently unknown. Several external stimuli, including high salinity, cause intracellular calcium ion (Ca2+) accumulation. Under salt stress, those ions form a specific long-distance signal that communicates responsiveness and adaptation messages between plant parts. However, while salt-induced Ca2+ signaling is known to mediate several adaptation events, its role in regulating pre-mRNA splicing is yet unknown. Here, evidence is presented that salt-induced long-distance Ca2+ signaling is involved in salt stress-regulated pre-mRNA splicing. Application of localized salt stress (NaCl) to Arabidopsis thaliana root tips modulates the expression and alternative splicing of several transcripts in the shoot. These transcript changes were inhibited by localized treatment of the mid-region of the root with LaCl3, a plasma-membrane Ca2+ channel blocker, suggesting salt-triggered Ca2+ signaling acts as a long-distance modulator of RNA transcription at both the levels of initiation and alternative pre-mRNA splicing. Interestingly, salt-induced Ca2+ signaling affects several stress-related pathways, including the Salt Overly Sensitive (SOS) and abscisic acid (ABA) signaling pathways, as well as expression of stress-associated genes and RNA splicing factors. These findings indicate the salt stress-activated long-distance calcium waves are involved in the molecular regulation of RNA splicing, which may contribute to entire-plant salt stress tolerance.