CAD enzyme activity and gene expression in connection with lignin synthesis during fruit development and ripening process of blackberry

【Objective】This study aimed to investigate the relationships among the expression profiles of cinnamyl alcohol dehydrogenase( CAD) genes,CAD enzyme activity,and total lignin content in fruit flesh from the fruit-setting to the mature stage of blackberry( Rubus spp.) cv.’Arapaho’and’Boysen’,which had relatively high and low firmness,respectively. 【Method】Expression profiles of Ru CAD genes in the fruit flesh of the two blackberry cultivars during the stages from coloring to maturity were detected using semi-quantitative RT-PCR. The changes in CAD enzyme activity and the lignin contents in fruit flesh were determined by colorimetric and titration methods,respectively. 【Result】During fruit development of the two cultivars,eight Ru CAD genes exhibited high expression level in the early and middle stages.Ru CAD16 was only detected in the early and middle stages in’Boysen’fruit flesh and not found in ’Arapaho’during any developmental stage. CAD enzyme activitly level in’Arapaho’and’Boysen’fruits was higher before coloring,specifically 9 DAF( days after flowering) and 21 DAF,and both declined after coloring. Total lignin content in the fruit flesh of both cultivars increased to relatively high level at 24 DAF and 27 DAF,respectively. 【Conclusion】After fruit coloring,expression level of Ru CAD genes exhibited various patterns,and the relationships among the fruit firmness,CAD enzyme activity and lignin content showed differences in fruits of’Arapaho’and’Boysen’. At late developmental stages,the fruit flesh of’Arapaho’and’Boysen’both showed similar declines in the expression level of Ru CAD genes,CAD enzyme activity,and total lignin contents,which was consistent with the decline in blackberry fruit firmness at maturity,implying a relationship between lignin synthesis and firmness in ripe fruits.