Evolutionary Conservation and Transcriptome Analyses Attribute Perenniality and Flowering to Day-Length Responsive Genes in Bulbous Barley (Hordeum bulbosum)

Abstract

Rapid population growth and dramatic climatic turnovers are challenging global crop production. These challenges are spurring plant breeders to enhance adaptation and sustainability of major crops. One intriguing approach is to turn annual systems into perennial, yet long-term classical breeding efforts to induce perenniality have achieved limited success. Here, we report results of our investigation of the genetic basis of bulb formation in the non-model organism Hordeum bulbosum, a perennial species closely related to barley. To identify candidate genes that regulate bulb formation in H. bulbosum we applied two complementary approaches. First, we explored the evolutionary conservation of expressed genes among annual Poaceae species. Next, we assembled a reference transcriptome for H. bulbosum and conducted a differential expression analysis before and after stimulating bulb initiation. Low conservation was identified in genes related to perenniality in H. bulbosum compared with other species, including bulb development and sugar accumulation genes. We also inspected these genes using a differential expression analysis, which enabled identification of additional genes responsible for bulb initiation and flowering regulation. We propose a molecular model for the regulation of bulb formation involving storage organ development and starch biosynthesis genes. The high conservation observed along most of the pathway between H. bulbosum and barley suggests a potential for application of biotechnological techniques to accelerate breeding towards perenniality in barley.