Identification of a PTC-containing DlRan transcript and its differential expression during somatic embryogenesis in Dimocarpus longan

Abstract

RAN (Ras-related nuclear protein) plays crucial roles in multiple cellular processes in yeast, animals and plants. Here we present a DlRan gene and its alternative splicing transcripts containing premature terminator codons (PTCs), identified from embryogenic cultures in longan. Multiple alignment and splicing pattern analyses indicated that DlRan-1 transcript harboring PTC was the consequence of alternative splicing. The accumulation of DlRan PTC-containing transcripts increased significantly when the embryogenic calli were treated with the translation inhibitor, cycloheximide, indicating that DlRan-1 may be targeted by NMD. The analysis of expression profiles of DlRan transcripts revealed that differential expression levels of the alternative spliced DlRan transcripts occurred during the development of embryogenic callus, globular-shaped embryos, and cotyledon-shaped embryos, respectively, in the longan somatic embryogenesis, and were in consistent with the embryo development in corresponding wild-type transcripts. The present work offers evidence to speculate that the alternatively spliced PTC-containing transcripts can be functional and may shed light on expression regulation of DlRan during development of the longan somatic embryos.

Keywords: 2,4-D; 2,4-dichlorophenoxyacetic acid; AS-NMD; CE; CHX; Dimocarpus longan; EC; GE; LEAFY COTYLEDON; LEC; NMD; Nonsense-mediated mRNA decay (NMD); PTC; Premature termination codon (PTC); RACE; RAN; RAN GTPase-activating protein; RANGAP1; RCC1; RT-PCR; Rapid amplification of cDNA ends; Ras-related nuclear protein; SE; SE receptor-like kinases; SERK; SMG; Somatic embryogenesis (SE); Suppressor with Morphogenetic effects on Genitalia; UPF; Up-stream frameshift; alternative splicing coupled with NMD; cotyledon-shaped embryos; cycloheximide; embryogenic callus; globular-shaped embryos; nonsense-mediated mRNA decay; premature terminator codons; regulator of chromosome condensation 1; reverse transcription polymerase chain reaction; somatic embryogenesis.