Identification and functional analysis of the TOPLESS-related co-repressor CcTPR4 in jute: a negative regulator of fiber yield through modulation of cellulose biosynthesis and gibberellin homeostasis

The TOPLESS/TOPLESS-related (TPL/TPR) gene family functions as pivotal transcriptional co-repressors in plants; however, its role in jute ( Corchorus L.), a major bast fiber crop, remains largely unexplored. In this study, we systematically identified 18 TPL/TPR family members in the jute genome. Candidate gene association studies pinpointed CcTPR4 as the sole gene within this family exhibiting a ‌significant association with fiber yield traits‌. Subcellular localization confirmed CcTPR4 as a nuclear protein, and its expression levels were ‌negatively correlated with plant height‌ in a natural population. Functionally, overexpression of CcTPR4 in jute roots significantly downregulated key cellulose synthase genes ( CcCesA4 , CcCesA7 , CcCesA8 ) and their transcriptional regulators ( CcMYB46 / 83 ). Conversely, virus-induced gene silencing of its ‌homolog in the bimli-jute‌ resulted in the upregulation of cellulose synthase genes ( HcCesA7 / 8 ) and the gibberellin (GA) biosynthesis gene HcKAO , concomitant with the downregulation of the GA catabolism gene HcGA2ox1 . ‌This study provides the first functional characterization of the TPL/TPR family in jute and highlights CcTPR4 as a prime candidate gene for molecular breeding aimed at enhancing fiber yield.