Elucidating the role of lignin pathway genes and enzymes in determining the fibre quality traits in Tossa jute (Corchorus olitorius L.)

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Department of Agricultural Biotechnology, Bidhan Chandra Krishi Viswavidyalaya , Mohanpur , Nadia-741252
Jute plant, belongs to genus Corchorus, is the second most important fibre crop after cotton. The fibre of jute is bio degradable, eco-friendly and renewable in nature which can be utilized in the replacement of synthetic fibre. The quality of jute fibre decreases with higher levels of lignin and lower levels of cellulose content, which needs to be addressed and improved. The fibre quality linked genes reportedly found in two different biochemical pathways, namely, lignin biosynthesis including shikimate aromatic amino acid pathway, monolignol pathway and cellulose biosynthesis pathway. In order to get the molecular insights of the fibre biogenesis, the present study was aimed to elucidate the role of the enzymes as well as the genes involved in lig jute varieties viz, JRO 524, which is a popular jute variety with comparatively coarse fibre and JBO 1, which has finer fibre were selected. The comparative yield performances were observed along with 14 other genotypes collected from AINP, J&AF. The qualities of the fibre in respect of fibre fineness and bundle strength were also assessed. estimation of biochemical parameters (acid detergent fibre, cellulose, acid detergent lignin, total protein); enzymatic assay (phenylalanine ammonia lyase and cinnamyl alcohol dehydrogenase) and histochemical assay (primary, secondary phloic fibre bundle and S lignin detection) were also carried out. The relative expression of Coumarate 3-hydroxylase (C3H), Ferulate 5-hydroxylase (F5H) and Cellulose synthase (Ces) genes at different growth stages in the bark tissues of the two tested varieties was studied using qRT-PCR. The statistical significant differences in respect of the studied traits among the selected genotypes were found. The highest fibre weight/ plant and fibre % were recorded in JRO 524 among all the genotypes. Among the tested varieties, the plant height, basal diameter and fibre weight/ plant of JRO 524 were significantly higher than JBO 1. Based on the quality parameters, JBO 1 can be considered as fine fibre and JRO 524 can be termed as coarse fibre. The fibre weight/ plant was significantly and positively correlated with plant height, green weight/ plant, dry weight/ plant, number of nodes/ plant and stick weight/ plant as evident from correlation analysis. Based on cluster analysis, the 16 genotypes were grouped into 5 clusters where the selected two varieties belong to same cluster indicating lesser genetic diversity among them. In the bark tissue of JBO 1, the acid detergent fibre and acid detergent lignin content, PAL and CAD enzyme activities were significantly lower than JRO 524 at 30 Days after germination (DAG) and 60 DAG stages whereas cellulose content of the bark tissue of JBO 1 was significantly higher than JRO 524 at 60 DAG. On the basis of histochemical analysis, variations in the fibre cell morphology were found between the two varieties where the fibre cell bundles of JRO 524 were overall more dignified than JBO 1. Four genes viz, PAL, CAD, C3H and F5H involved in lignin biosynthesis and Ces gene involved in cellulose biosynthesis of tossa jute were recognized and functionally characterized by finding the molecular properties and by constructing phylogenetic trees along with other homologous genes of other organisms. Sequencing of the partial CDS of F5H gene of JRO 524 and JBO 1 was done and the CDSs were functionally characterized and submitted at NCBI (Accession nos: OP629814.1 and OP629813.1). Based on the qRT-PCR analysis, it was observed that that C3H gene involved in monolignol pathway, had significantly lower expression in the bark tissue of JBO 1 at both 30 DAG (0.43 fold) and 60 DAG (0.84 fold) in comparison with JRO 524, whereas, F5H gene involved in monolignol pathway, was significantly overexpressed (1.29 folds) in JBO 1 at 30 DAG and under expressed (0.51 fold) at 60 DAG. The Ces gene involved cellulose biosynthetic pathway was significantly expressed more at 30 DAG (1.08 folds) and expressed lesser at 60 DAG (0.75) compared to JRO 524. Thus, from the present study it is evident that the fine fibre in jute is attributed with more bundle strength, lower lignin content and lower activity of enzymes involved in lignin biosynthetic pathway, higher cellulose content, lower expression of C3H gene at both 30, 60 DAG, lower expression of F5H at 60 DAG along with higher Ces expression at 30 DAG.