Soluble acid invertase and sucrose phosphate synthase: Key enzymes in regulating sucrose accumulation in sugarcane stalk

Abstract

The present study was conducted to assess the relative importance of reducing sugar contents, soluble proteins and activities of four enzymes viz., soluble acid invertase (SAI), sucrose synthase (SS), neutral invertase (NI) and sucrose phosphate synthase (SPS) in regulation of sucrose accumulation during the growth and development of internodes in sugarcane (Saccharum spp. hybrids). Fourteen internodes from internode 2 to internode l5 were sampled from the stalks of the first ratoon crop of two sugarcane cultivars, i.e. ROC20 and RB72-454. The internodes were cut into small pieces and frozen in liquid nitrogen and then stored in −30°C freezer until used. Content of sucrose, reducing sugar, soluble protein and activities of SPS, SAI, SS and NI were assayed. The results of multiple regression and partial correlation analyses showed that the sucrose content was negative correlated with the content of the reducing sugar and soluble protein during the growth and development of the internodes. Path coefficient analysis and optimum combination regression equation showed that soluble protein was more important than reducing sugar in regulating the sucrose level in sugarcane internodes. The sucrose content was positively correlated with the activity of SPS and negatively correlated with the activities of SAI, SS and NI in the both cultivars, but only the SAI in ROC20 and SAI and SPS in RB72-454 were significant at the level 0.05 in T-test for the optimum combination regression equation. Soluble protein was more important than reducing sugar in regulating sucrose accumulation in sugarcane internodes. SAI and SPS were the key enzymes in regulating sucrose accumulation during the growth and development of the internodes of sugarcane stalk. The results of the present study provided references for further research on regulating the sucrose accumulation in sugarcane stalk at molecular level.