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Sucrose-Phosphate Synthase, a Biochemical Marker of High Sucrose Accumulation in Sugarcane

CSIRO Plant Industry, Queensland Bioscience Precinct, 306 Carmody Rd., St Lucia QLD 4067, Australia

View larger version (31K): [in this window] [in a new window]   Figure 1. Sucrose concentrations in selected internodes on a fresh mass basis for (a) four high and four low commercial cane sugar (CCS) clones from the introgression population (IJ76-514 x Q165) and (b) eight clones from the backcross population (KQ99-1410 x Mida). Each point is the mean ± SE of three measurements. Internode middle denotes that position midway between internode 10 and the bottom of the stalk. FW, fresh weight.

View larger version (24K): [in this window] [in a new window]   Figure 2. The sucrose/hexose ratio in selected internodes from four high and four low commercial cane sugar (CCS) clones from (a) the introgression population (IJ76-514 x Q165) and from (b) eight clones from the backcross population (KQ99-1410 x Mida). Each point is the mean ± SE of three measurements. Internode middle denotes that position midway between internode 10 and the bottom of the stalk.

View larger version (15K): [in this window] [in a new window]   Figure 3. Activity of key enzymes in high (¡) and low (l) commercial cane sugar (CCS) clones from introgression population, IJ76-514 x Q165. Measurements performed in the first series (a–c); measurements performed in the second series (d–f). Panels a and d are sucrose-phosphate synthase; b and e, neutral invertase; and c and f, soluble acid invertase. The units of activity are µg sucrose formed mg –1 protein min–1 in a and d; µg sucrose cleaved mg –1 protein min–1 in b, c, e, and f. Each point is the mean ± SE of six measurements.

View larger version (12K): [in this window] [in a new window]   Figure 4. Changes in enzyme activities measured at four positions down the stem in two high (¡) and two low (l) commercial cane sugar (CCS) clones selected from the IJ76-514 x Q165 introgression population. Each point is the mean ± SE of six measurements. Activity of sucrose synthase forward (a) is expressed as µg sucrose produced mg protein–1 min–1 whereas sucrose synthase reverse (b) is expressed as sucrose cleaved mg protein–1 min–1. Cell wall invertase activity (c) is expressed as ng sucrose cleaved g FW–1 min–1.

View larger version (11K): [in this window] [in a new window]   Figure 5. Sucrose-phosphate synthase (SPS) activity in the uppermost internodes (1 + 2 + 3) of eight clones from the backcross population KQ99-1410 x Mida plotted against whole stalk commercial cane sugar (CCS) measured at final harvest. Individual values are for one replicate of a single clone. The values in open squares are for clone KQ01–3060 for which one CCS value was much lower than the others. The equation for the regression line shown, SPS = 0.1435CCS – 1.1638 (r2 = 0.371, P < 0.003) is for all of the plotted data.