Transcriptional and Hormonal Regulation of Weeping Trait in Salix matsudana

Abstract

Salix matsudana is a large and rapidly-growing tree, with erect or spreading branchlets (upright willow). However, S. matsudana var. pseudomatsudana is one of the varietas, with pendulous branchlets (weeping willow). It has high ornamental value for its graceful pendulous branches. In order to study the molecular basis for this weeping trait, leaves and stems collected at different developmental stages were analyzed using RNA-seq coupled with digital gene expression. Although weeping trees are used worldwide as landscape plants, little is known about the genes that control weeping. Our growth results indicated that branches in weeping willow developed and elongated throughout all developmental stages, but branches in upright willow grew rapidly in the initial stages and then grew slowly and began shoot branching in the middle stages. A total of 613 hormone-related genes were differentially expressed in willow development. Among these, genes associated with auxin and gibberellin (GA) were highly likely to be responsible for the weeping trait, and genes associated with auxin and ethylene probably play crucial roles in shoot elongation. The genes with differential expression patterns were used to construct a network that regulated stem development, and auxin-related genes were identified as hub genes in the network in the weeping willow. Our results suggest an important role of gibberellin and auxin in regulating the weeping trait in Salix matsudana. This is the first report on the molecular aspects of hormonal effects on weeping trait in willow using transcriptomics and helps in dissecting the molecular mechanisms by which the weeping trait is controlled.

Transcriptomic Analysis Reveals Hormonal Control of Shoot Branching in Salix matsudana

“…The library was sequenced on an Illumina HiSeq TM 2000 platform (Illumina, San Diego, CA, USA). Transcript quantification from RNA-Seq data was performed in a previous study [46]. In each DGE library, tag sequences were mapped to the reference sequences generated in the RNA-Seq-based transcriptome.…”

“…The expression of each gene was normalized to the expected number of Fragments Per Kilobase of transcript sequence per Millions base pairs sequenced (FPKM). Quantitative real-time PCR (qRT-PCR) analysis was performed to validate the expression levels of DEGs from RNA-Seq and DGE data in a previous study [46]. Based on the quantification of transcript results, nine pairwise comparisons in six DGE libraries of the two willow species at two developmental stages using two different branch portions were analyzed.…”

“…Willows (Salix spp.) are one of the most important bio-energetic and ornamental plants worldwide [2,46]. Two willow species, S. matsudana (SM) and S. matsudana var.…”

Transcriptome profiles reveal that gibberellin-related genes regulate weeping traits in crape myrtle

“…In peach, the pl phenotype may be associated with GA signaling and upright branch internodes are shorter than those of weeping branches in peach, implying that the upright type may have a lower GA content 27 . Transcriptional results suggest that GA and auxin play a vital role in controlling the weeping trait in Salix matsudana 28 . Transcriptome analysis of columnar apple trees showed that genes associated with auxin and GA, such as xyloglucan endotransglycosylase (XTH) and gibberellin 2β-dioxygenase 1 (GA2ox1), are located in the Co region linked with the apple column trait 29 .…”

Production and characterization of intersectional hybrids between <i>Tricyrtis</i> sect. <i>Brachycyrtis</i> and sect. <i>Hirtae</i> via ovule culture

“…Since all of the intersectional hybrids investigated in the present study had semi-cascade-type shoots, the shoot pattern in Tricyrtis may be a semi-dominant trait. In Prunus spachiana (Nakamura et al 1994) and Salix matsudana (Liu et al 2017), weeping shoot traits are regulated by the endogenous gibberellin level. It is necessary to analyze the endogenous gibberellin level in Tricyrtis plants with erect-, semi-cascade-and cascadetype shoots.…”