The contribution of sucrose metabolism enzymes to sucrose accumulation in sugarcane (Saccharum officinarum L.) genotypes

Abstract

Increasing sugar content is the primary objective of sugarcane (Saccharum officinarum L.) improvement programs. To assess the importance of sucrose metabolizing enzymes in relation to sucrose content, enzymatic profiles of sucrose phosphate synthase (SPS), sucrose synthase (SuSy), acid and neutral invertases (AI and NI) were analyzed in relation to total sugars and reducing sugars in different sugarcane genotypes at 300, 360 and 420 days after planting (DAP). Varying responses in enzymatic profiles in relation to sugar content were noticed. The activities of SPS exceeded that of SuSy, AI and NI at 360 DAP, while SuSy was dominant at 420 DAP. Total sugars content were highest at 360 DAP and then declined at 420 DAP. Reducing sugars increased gradually from 300 to 420 DAP. Significant negative and positive correlations of SPS with reducing sugars and total sugars, respectively were noticed at 360 DAP. Interestingly, NI was strongly associated with reducing sugars, total sugars and ratio of total sugars to reducing sugars at 360 DAP as compared to AI. Differences between SPS–AI and SPS–NI exhibited significant negative correlation with reducing sugars and positive correlation with total sugars at 360 DAP. Differences between SPS–NI explained most of the variations found for sucrose accumulation in sugarcane. Our data demonstrate that synthesis and breakdown of sugars in sugarcane tissue is coordinated by the activities of AI, NI and SPS, respectively.