Comprehensive profiling of rhizome-associated alternative splicing and alternative polyadenylation reveals in moso bamboo (Phyllostachys edulis). Phyllostachys edulis

Moso bamboo (Phyllostachys edulis) represents one of the fastest-spreading plants in the world, due in part to their well-developed rhizomes system. However, the post-transcriptional regulation mechanism has not been comprehensively studied for the development of rhizome system in bamboo. We therefore used single-molecule long-read sequencing technology to re-annotate the bamboo genome, and genome-wide identify alternative splicing (AS) and alternative polyadenylation (APA) in the rhizomes system. In total, 145,522 mapped full-length non-chimeric (FLNC) reads were analyzed, resulting in the correction of 2,241 mis-annotated genes and identification of 8,091 previously unannotated loci. Markedly, more than 42,280 contiguous exon connectivity were derived from full-length splicing isoforms, including a large number of AS events that associated with rhizome systems. In addition, we characterized 25,069 polyadenylation sites from 11,450 genes, 6,311 of which have APA sites. Further analysis of intronic polyadenylation revealed that LTR/Gypsy and LTR/Copia were two major transposable elements (TEs) within the intronic polyadenylation region. Furthermore, this study provided a quantitative altas of poly(A) usage and identified several hundreds of differential poly(A) sites in rhizome-root system using a combination of polyadenylation site sequencing (PAS-seq) and PacBio reads. Taken together, these results suggest that posttranscriptional regulation may potentially play vital role in the underground rhizome-root system. Overall design: Single-molecule long-read sequencing, PAS-seq and RNA-seq of leptomorph rhizome tip, new shoot tip and bud