De novo Whole Transcriptome Analysis of Wingpod Purslane, Portulaca umbraticola, and Its Application to the Discovery of Genes Related to Flower Senescence and Opening Rhythm

抄録

Portulaca umbraticola, an important ephemeral summer bedding plant, may be a model system for studies on flowering behavior under heat stress. Herein, we report the first comprehensive transcriptome analysis of P. umbraticola by RNA-sequencing. We generated 22.15 G bases which were assembled into 68,928 unigenes, and a total of 43,880 coding sequences (CDS) were detected. We also detected 13,603 simple sequence repeats on 10,784 unigenes, and predicted 1,444 transcription factor (TF) coding unigenes. Subsequently, we focused on gene discovery in the areas of flower senescence and opening rhythm. We identified the majority of transcripts involved in ethylene biosynthesis, perception, and signaling pathways, as well as transcripts corresponding to circadian clock components. Expression profiles of the ethylene biosynthesis and signaling pathway genes in two cultivars with different flower longevity showed a clear correlation with previously observed endogenous ethylene production. PuACS1 and PuACO2 transcripts showed higher expression, and peaked earlier in a short lived cultivar than in a long lived cultivar. Expression analysis of the core clock component genes showed PuCCA1/PuLHY and PuTOC1 under reciprocal circadian regulation similar to that found in Arabidopsis thaliana, and other plant species. This study provides the first steps in understanding the molecular mechanisms underlying flowering traits in P. umbraticola, and paves the way for future integrated insights into molecular genetics, biotechnology and physiological studies of P. umbraticola.