Starch granules in tomato fruit show a complex pattern of degradation

Starch is transiently accumulated in tomato fruit with near complete degradation achieved by maturity. Surprisingly, (14)C-pulse-chase analyses indicated that the rate of starch degradation was highest in immature fruit [10 days post anthesis (DPA)] when maximal synthesis occurs, but was almost undetectable at 45 DPA when there is net breakdown of starch. Further analysis of starch accumulation, rate of synthesis, particle size analysis, and confocal laser scanning microscopy of starch granules from developing fruit suggests that the rate of starch degradation does increase after 40 DPA, but it may not occur at the same site at which starch is synthesized. Furthermore, the degradation rate at maturity is lower than that measured in early development. Overall, the results suggest that starch degradation in developing tomato is biphasic with separate regiotemporal occurrences. This mechanism may have evolved to offer flexibility in balancing starch accumulation and utilization in the developing fruit.