Interconversions of reserve carbohydrates from pollen maturation to rehydration in a chili pepper

CARRIZO GARCÍA C, GUARNIERI M, PACINI E

Bristol

Congreso; XXI International Congress on Sexual Plant Reproduction; 2010

International Association of Sexual Plant Reproduction Research

In pollen grains there are several carbohydrates that may function as reserves, which are involved in different processes during pollen maturation, presentation and germination. Therefore, the regulation of the carbohydrates metabolism is critical for the male fertility. The content of reserve carbohydrates was described in three stages of pollen development (bicellular, mature, and rehydrated), to analyze the possible interconversions between them. The activity of four soluble enzymes involved in those interconversions was quantified in the same stages to reveal the possible metabolic pathways followed. The study was done in a chili pepper variety (Capsicum annuum) with partially dehydrated (desiccation resistant) pollen. The main soluble carbohydrates found were sucrose, glucose and fructose, which increased in different degrees through pollen maturation; sucrose was consumed during rehydration while glucose and fructose remained almost unchanged. Pectic walls were deposited in the etipsf formed during rehydration (neither callose nor cellulose were detected). In general, the activity of sucrolytic enzymes (invertases and sucrose synthase) increased from the bicellular stage to the mature pollen, and later decreased in parallel with sucrose depletion during rehydration. Soluble invertases carried out most of sucrose hydrolysis. The abundant starch found at the bicellular stage was almost completely hydrolized afterwards. Amylases activities decreased while starch concentration was reduced. According to the products of hydrolysis, ƒ¿- and ƒÀ-amylase activities would change along stages. It seems to be an interconversion between the carbohydrates analyzed, whose changes in concentration are apparently related with the level of activity of the enzymes studied. All these enzymes seem to be actively involved, in different and variable degrees between stages, along pollen maturation and rehydration.