DROL1 subunit of U5 snRNP in the spliceosome is specifically required to splice AT–AC-type introns in Arabidopsis

Abstract

SummaryAn Arabidopsis mutant named defective repression of OLE3::LUC 1 (drol1) was originally isolated as a mutant with defects in the repression of OLEOSIN3 (OLE3) after seed germination. In this study, we show that DROL1 is an Arabidopsis homolog of yeast DIB1, a subunit of U5 snRNP in the spliceosome. It is also part of a new subfamily that is specific to a certain class of eukaryotes. Comprehensive analysis of the intron splicing using RNA-Seq analysis of the drol1 mutants revealed that most of the minor introns with AT–AC dinucleotide termini had reduced levels of splicing. Only two nucleotide substitutions from AT–AC to GT–AG enabled AT–AC-type introns to be spliced in drol1 mutants. Forty-eight genes, including those having important roles in abiotic stress responses and cell proliferation, exhibited reduced splicing of AT–AC-type introns in the drol1 mutants. Additionally, drol1 mutant seedlings showed retarded growth, similar to that caused by the activation of abscisic acid signaling, possibly as a result of reduced AT–AC-type intron splicing in the endosomal Na+/H+ antiporters and plant-specific histone deacetylases. These results indicate that DROL1 is specifically involved in the splicing of minor introns with AT–AC termini, and that this plays an important role in plant growth and development.Significance statementDefective Repression of OLE3::LUC 1 (DROL1) is a homolog of yeast DIB1, which is a subunit of the U5 snRNP in the spliceosome, but is also part of a new subfamily that is specific to a certain class of eukaryotes. Using RNA-Seq we show that introns with AT–AC dinucleotide termini were specifically retained in the transcriptome of drol1 mutants and that their splicing plays an important role in plant growth and development.