A chromosome-level genome assembly of Amorphophallus konjac provides insights into konjac glucomannan biosynthesis

Abstract

<i>Amorphophallus konjac</i>, a perennial herb in the Araceae family, is a cash crop that can produce a large amount of konjac glucomannan. To explore mechanisms underlying such large genomes in the genus <i>Amorphophallus</i> as well as the gene regulation of glucomannan biosynthesis, we present a chromosome-level genome assembly of <i>A. konjac</i> with a total genome size of 5.60 Gb and a contig N50 of 1.20 Mb. Comparative genomic analysis reveals that <i>A. konjac</i> has undergone two whole-genome duplication (WGD) events in quick succession. Two recent bursts of transposable elements are identified in the <i>A. konjac</i> genome, which contribute greatly to the large genome size. Our transcriptomic analysis of the developmental corms characterizes key genes involved in the biosynthesis of glucomannan and related starches. High expression of cellulose synthase-like A, Cellulose synthase-like D, mannan-synthesis related 1, GDP-mannose pyrophosphorylase and phosphomannomutase fructokinase contributes to glucomannan synthesis during the corm expansion period while high expression of starch synthase, starch branching enzyme and phosphoglucomutase is responsible for starch synthesis in the late corm development stage. In conclusion, we generate a high-quality genome of <i>A. konjac</i> with different sequencing technologies. The expansion of transposable elements has caused the large genome of this species. And the identified key genes in the glucomannan biosynthesis provide valuable candidates for molecular breeding of this crop in the future.