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Summary Kenaf is an annual crop that is widely cultivated as a source of bast (phloem) fibres, the phytoremediation of heavy metal‐contaminated farmlands and textile‐relevant compounds. Leaf shape played a unique role in kenaf improvement, due to the inheritance as a single locus and the association with fibre development in typical lobed‐leaf varieties. Here we report a high‐quality genome assembly and annotation for var. ‘Fuhong 952’ with 1078 Mbp genome and 66 004 protein‐coding genes integrating single‐molecule real‐time sequencing, a high‐density genetic map and high‐throughput chromosome conformation capture techniques. Gene mapping assists the identification of a homeobox transcription factor LATE MERISTEM IDENTITY 1 (HcLMI1) gene controlling lobed‐leaf. Virus‐induced gene silencing (VIGS) of HcLMI1 in a lobed‐leaf variety was critical to induce round (entire)‐like leaf formation. Candidate genes involved in cell wall formation were found in quantitative trait loci (QTL) for fibre yield and quality‐related traits. Comparative genomic and transcriptome analyses revealed key genes involved in bast fibre formation, among which there are twice as many cellulose synthase A (CesA) genes due to a recent whole‐genome duplication after divergence from Gossypium. Population genomic analysis showed two recent population bottlenecks in kenaf, suggesting domestication and improvement process have led to an increase in fibre biogenesis and yield. This chromosome‐scale genome provides an important framework and toolkit for sequence‐directed genetic improvement of fibre crops.

Kenaf is one of the most important natural fiber crops. The lack of molecular markers has resulted in a large gap in the improvement of kenaf. Previously, de novo 90,175 unigenes in kenaf were assembled. In this study, 7453 small InDels were called from these uingenes. The indel size 10 bp have frequencies of 71.50%, 23.05%, and 5.45%. 337 InDels locating in genes encoding transcription factors were used to survey polymorphisms with 24 kenaf accessions. Of 337 InDels, 305 (90.5%) successfully amplified at least one fragment and detected polymorphism among the 24 diverse genotypes. Furthermore, one InDel marker, HcID266, was co-segregated with leaf shape, which was inherited as a single Mendelian locus, in the F2 population with 390 individuals. To our knowledge, this is the first large-scale InDels development for kenaf. These InDel markers will be helpful for genetic researches in kenaf.

Background WRKY is a group of transcription factors (TFs) that play a vital role in plant growth, development, and stress tolerance. To date, none of jute WRKY (CcWRKY) genes have been identified, even if jute (Corchorus capsularis) is one of the most important natural fiber crops in the world. Little information about the WRKY genes in jute is far from sufficient to understand the molecular mechanism of bast fiber biosynthesis. Results A total of 244,489,479 clean reads were generated using Illumina paired-end sequencing. De novo assembly yielded 90,982 unigenes with an average length of 714 bp. By sequence similarity searching for known proteins, 48,896 (53.74%) unigenes were annotated. To mine the CcWRKY TFs and identify their potential function, the search for CcWRKYs against the transcriptome data of jute was performed, and a total of 43 CcWRKYs were identified in this study. The gene structure, phylogeny, conserved domain and three-dimensional structure of protein were analyzed by bioinformatics tools of GSDS2.0, MEGA7.0, DNAMAN5.0, WebLogo 3 and SWISS-MODEL respectively. Phylogenetic analysis showed that 43 CcWRKYs were divided into three groups: I, II and III, containing 9, 28, and 6 members respectively, according to the WRKY conserved domain features and the evolution analysis with Arabidopsis thaliana. Gene structure analysis indicated that the number of exons of these CcWRKYs varied from 3 to 11. Among the 43 CcWRKYs, 10, 2, 2, and 14 genes showed higher expression in leaves, stem sticks, stem barks, and roots at the vigorous vegetative growth stage, respectively. Moreover, the expression of 21 of 43 CcWRKYs was regulated significantly with secondary cell wall biosynthesis genes using FPKM and RT-qPCR by GA3 stress to a typical GA3 sensitive dwarf germplasm in comparison to an elite cultivar in jute. The Cis-element analysis showed that promoters of these 21 CcWRKYs had 1 to 4 cis-elements involved in gibberellin-responsiveness, suggesting that they might regulate the development of bast fiber in response to GA3 stress. Conclusions A total of 43 CcWRKYs were identified in jute for the first time. Analysis of phylogenetic relationship and gene structure revealed that these CcWRKYs might have a functional diversity. Expression analysis showed 21 TFs as GA3 stress responsive genes. The identification of these CcWRKYs and the characterization of their expression pattern will provide a basis for future clarification of their functions in bast fiber development in jute.

Background WRKY transcription factor is a kind of transcription factor which plays an important role in plant response to biotic, abiotic stress, plant growth and development. However, little information was available about the WRKY genes in jute ( Corchorus capsularis ).Results In the present study, 43 jute WRKY (CcWRKY) genes were identified by using Pfam database domain search and BLAST homology alignment based on the transcriptome data of jute. And the gene structure, phylogeny, conserved domain and three-dimensional structure of protein were also analyzed by GSDS2.0, MEGA7.0, DNAMAN5.0, WebLogo 3 and SWISS-MODEL bioinformatics tools. According to the WRKY conserved domain features and the evolution analysis with Arabidopsis thaliana , 43 members were divided into three classes: I, II and III containing 9, 28, 6 members, respectively. According to the evolutionary relationship, class II further divided into five subclasses: II-a (2), II-b (7), II-c (7), II-d (6) and II-e (6). Genetic structure analysis showed that exon and intron number of CcWRKY genes had high variability (3-11 exons), even within the same subgroup. Most of the CcWRKY genes were expressed in different tissues, but they were mainly expressed in stem bark and stem stick. After GA 3 stress, the expression of most WRKY genes in GA 3 -sensitive variety "Aidianyehuangma" was significantly different from that of normal variety "Huangma 179". These results indicated that CcWRKY genes play an important role in gibberellin biosynthesis pathway and fiber development.Conclusions CcWRKY proteins are highly conserved, the length of the gene sequence and the number of introns varied widely, all WRKY genes showed a variety of expression patterns in different tissues, most of the WRKY genes responded to GA 3 stress, which play an important role in gibberellin biosynthesis pathway and bast fiber development.

Jute, including white and dark jute, is an agroeconomically important fiber crop worldwide. However, no practical information is available for expressed sequence tag-derived InDel (insertion and deletion) in jute to date. Previously, we de novo assembled 48,914 unigenes from white jute. In this study, 4815 InDels were called from these unigenes. The size

Background WRKY transcription factor is a kind of transcription factor which plays an important role in plant response to biotic, abiotic stress, plant growth and development. However, little information was available about the WRKY genes in jute ( Corchorus capsularis ).Results In the present study, 43 jute WRKY (CcWRKY) genes were identified by using Pfam database domain search and BLAST homology alignment based on the transcriptome data of jute. And the gene structure, phylogeny, conserved domain and three-dimensional structure of protein were also analyzed by GSDS2.0, MEGA7.0, DNAMAN5.0, WebLogo 3 and SWISS-MODEL bioinformatics tools. According to the WRKY conserved domain features and the evolution analysis with Arabidopsis thaliana , 43 members were divided into three classes: I, II and III containing 9, 28, 6 members, respectively. According to the evolutionary relationship, class II further divided into five subclasses: II-a (2), II-b (7), II-c (7), II-d (6) and II-e (6). Genetic structure analysis showed that exon and intron number of CcWRKY genes had high variability (3-11 exons), even within the same subgroup. Most of the CcWRKY genes were expressed in different tissues, but they were mainly expressed in stem bark and stem stick. After GA 3 stress, the expression of most WRKY genes in GA 3 -sensitive variety "Aidianyehuangma" was significantly different from that of normal variety "Huangma 179". These results indicated that CcWRKY genes play an important role in gibberellin biosynthesis pathway and fiber development.Conclusions CcWRKY proteins are highly conserved, the length of the gene sequence and the number of introns varied widely, all WRKY genes showed a variety of expression patterns in different tissues, most of the WRKY genes responded to GA 3 stress, which play an important role in gibberellin biosynthesis pathway and bast fiber development.

Kenaf (Hibiscus cannabinus) is one of important nature fiber crops in the world. However, the EST sequence resources available for kenaf are still very limited. In this study, 131,262,686 clean reads (13.12 Gb) using Illumina paired-end sequencing were assembled. De novo assembly yielded 90,175 unigenes with an average length of 700 bp. By sequence similarity searching for known proteins, 46,165 (51.19 %) unigenes were annotated for their function. Out of these annotated unigenes, 37,080 (41.12 %) unigenes showed significant similarity to genes of a diploid cotton (Gossypium raimondii). Searching against the Kyoto encyclopedia of genes and genomes (KEGG) indicated that 23,051 unigenes were mapped to 254 KEGG pathways, and 317 genes were assigned to starch and sucrose metabolic pathway which was related with cellulose biosynthesis. Furthermore, a total of 52,521 putative gene-associated SNPs and 11,083 SSRs (designated as HcEMS) were identified from these assembled unigenes. Among these HcEMS markers, mono-, di-, and trinucleotide repeat types were the most abundant types (40.3, 22.3, and 34.7 %, respectively). The AG-rich nucleotide repeats, including (AG)n, (AAG)n, and (AAAG)n types, were the most abundant and could be considered as the dominant types in kenaf. A sample of 835 HcEMSs were used to survey polymorphisms with eight kenaf accessions. Of them, 753 (90.1 %) successfully amplified at least one fragment and 450 (53.9 %) detected polymorphism. All these results will accelerate the understanding of genetic basis of the fiber development and marker-assisted breeding in kenaf.