Journal Article

Genome-wide transcriptome profiling of transgenic hop (Humulus lupulus L.) constitutively overexpressing HlWRKY1 and HlWDR1 transcription factors

J. Bříza, Jernej Jakše, Jaroslav Matoušek, Josef Patzak, Ganesh Selvaraj Duraisamy, Tomáš Kocábek, Mudra Khare, Teruo Sano, Ajay Kumar Mishra

2018

Overview

Background The hop plant ( Humulus lupulus L.) is a valuable source of several secondary metabolites, such as flavonoids, bitter acids, and essential oils. These compounds are widely implicated in the beer brewing industry and are having potential biomedical applications. Several independent breeding programs around the world have been initiated to develop new cultivars with enriched lupulin and secondary metabolite contents but met with limited success due to several constraints. In the present work, a pioneering attempt has been made to overexpress master regulator binary transcription factor complex formed by Hl WRKY1 and Hl WDR1 using a plant expression vector to enhance the level of prenylflavonoid and bitter acid content in the hop. Subsequently, we performed transcriptional profiling using high-throughput RNA-Seq technology in leaves of resultant transformants and wild-type hop to gain in-depth information about the genome-wide functional changes induced by Hl WRKY1 and Hl WDR1 overexpression. Results The transgenic WW-lines exhibited an elevated expression of structural and regulatory genes involved in prenylflavonoid and bitter acid biosynthesis pathways. In addition, the comparative transcriptome analysis revealed a total of 522 transcripts involved in 30 pathways, including lipids and amino acids biosynthesis, primary carbon metabolism, phytohormone signaling and stress responses were differentially expressed in WW-transformants. It was apparent from the whole transcriptome sequencing that modulation of primary carbon metabolism and other pathways by Hl WRKY1 and Hl WDR1 overexpression resulted in enhanced substrate flux towards secondary metabolites pathway. The detailed analyses suggested that none of the pathways or genes, which have a detrimental effect on physiology, growth and development processes, were induced on a genome-wide scale in WW-transgenic lines. Conclusions Taken together, our results suggest that Hl WRKY1 and Hl WDR1 simultaneous overexpression positively regulates the prenylflavonoid and bitter acid biosynthesis pathways in the hop and thus these transgenes are presented as prospective candidates for achieving enhanced secondary metabolite content in the hop.

• Publisher: Springer Science and Business Media LLC,BioMed Central,Springer Nature B.V,BMC
• Subject: Amino acids / Ammonia / Animal Genetics and Genomics / Applications programs / Beer / Biomedical and Life Sciences / Biomedical materials / Biosynthesis / Biotechnology / Bitter acids / Brewing / Carbon / Cultivars / Enzymes / Essential oils / Flavonoids / Gene Expression / Gene Expression Profiling / Genes / Genetic transformation / Genetics / Genomes / Genomics / Humulus / Humulus - genetics / Humulus lupulus / Kinases / Life Sciences / Lipid metabolism / Lipids / Metabolism / Metabolites / Microarrays / Microbial Genetics and Genomics / Molecular Sequence Annotation / Oils & fats / Plant Genetics and Genomics / Plant genomics / Plant hormones / Plant Proteins / Plant Proteins - genetics / Plants, Genetically Modified / Proteins / Proteomics / QH426-470 / Research Article / Ribonucleic acid / RNA / Secondary metabolite / Secondary metabolites / Substrates / TP248.13-248.65 / Transcription factors / Transcription Factors - genetics / Transgenes