Pre-mRNA splicing regulates cellular dedifferentiation via lipid metabolism in a cytokinin-dependent manner in Arabidopsis.

Abstract

Plant cells exhibit high plasticity for proliferation and differentiation, and pre-mRNA splicing makes an important contribution to this plasticity. Here, we show that the gene responsible for root redifferentiation defective4-1 (rrd4-1), a temperature-sensitive Arabidopsis thaliana mutant with defects in adventitious rooting and callus formation from hypocotyls, encodes a homolog of yeast Ntr1, which is involved in pre-mRNA splicing. Defective callus formation in rrd4-1 at the restrictive temperature of 28°C depended on the presence of kinetin (a synthetic cytokinin) in the callus-inducing medium. RNA-seq analysis revealed that genes involved in secondary cell wall biogenesis were upregulated, whereas those involved in cell cycle progression were downregulated, in a cytokinin-dependent manner in rrd4-1 at 28°C. Moreover, kinetin and the rrd4-1 mutation had broad effects on alternative splicing, particularly on lipid metabolism genes such as PTPLA, SPHK2, and ATNCER1. Consistent with this result, levels of very-long-chain fatty acid (VLCFA)-type sphingolipids were reduced in rrd4-1, and kinetin affected their contents during callus induction. Kinetin enhanced the inhibitory effect of the lipid synthesis inhibitor cerulenin on callus formation, and rrd4-1 was hypersensitive to cerulenin. Together, our data suggest that pre-mRNA splicing regulates cytokinin-mediated cellular dedifferentiation through the regulation of lipid metabolism gene splicing.