Sucrose and starch catabolism in the anther of Lilium during its development: a comparative study among the anther wall, locular fluid and microspore/pollen fractions

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Abstract
In order to better understand the various pathways of sucrose and starch catabolism in the anther of lily (Lilium hybrida var. “Enchantment”), invertase (EC 3.2.1.26) and amylase (EC 3.2.1.1, EC 3.2.1.2) activities were measured separately in different fractions (anther wall, locular fluid and microspore/pollen) and correlated with the sugar content during anther development. Our findings showed significant differences among the fractions analyzed, suggesting that the regulation of sucrose and starch catabolism could follow distinct pathways in each fraction. Glucose and fructose amounts progressively decreased from anther wall to fluid and from fluid to microspore/pollen. Thus, the developing pollen could act as a sink for the carbohydrates that reach the anther. In this sense, cell wall-bound invertases seem to play a major role in soluble sugar partitioning in the different fractions of the anther. Sucrose concentration was found to be substantially higher in the locular fluid than in the other fractions, indicating a probable site for storage. On the other hand, the anther wall tissues could have a buffering function, storing nutrient surplus in starch grains and thus regulating the availability of soluble sugars in the whole anther. All these results proved the advantages of the experimental model proposed here, as well as its usefulness to investigate sugar metabolism in Lilium anthers.