Dual roles of the serine/arginine-rich splicing factor SR45a in promoting and interacting with nuclear cap-binding complex to modulate the salt-stress response in Arabidopsis.

Affiliation

Li Y(1), Guo Q(1), Liu P(2), Huang J(1), Zhang S(1), Yang G(1), Wu C(1), Zheng C(1), Yan K(1).
Author information:
(1)State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Taian, Shandong, 271018, China.
(2)Donald Danforth Plant Science Center, St Louis, MO, 63132, USA.

Abstract

Alternative splicing (AS) is emerging as a critical co-transcriptional regulation for plants in response to environmental stresses. Although multiple splicing factors have been linked to the salt-sensitive signaling network, the molecular mechanism remains unclear. We discovered that a conserved serine/arginine-rich (SR)-like protein, SR45a, as a component of the spliceosome, was involved in post-transcriptional regulation of salinity tolerance in Arabidopsis thaliana. Furthermore, SR45a was required for the AS and messenger RNA (mRNA) maturation of several salt-tolerance genes. Two alternatively spliced variants of SR45a were induced by salt stress, full-length SR45a-1a and the truncated isoform SR45a-1b, respectively. Lines with overexpression of SR45a-1a and SR45a-1b exhibited hypersensitive to salt stress. Our data indicated that SR45a directly interacted with the cap-binding complex (CBC) subunit cap-binding protein 20 (CBP20) which mediated salt-stress responses. Instead of binding to other spliceosome components, SR45a-1b promoted the association of SR45a-1a with CBP20, therefore mediating salt-stress signal transduction pathways. Additionally, the mutations in SR45a and CBP20 led to different salt-stress phenotypes. Together, these results provide the evidence that SR45a-CBP20 acts as a regulatory complex to regulate the plant response to salt stress, through a regulatory mechanism to fine-tune the splicing factors, especially in stressful conditions.