Alessandro Baldicchi

Soluble sugar and organic acid contents and the occurrence and potential role of phosphoenolpyruvate carboxykinase (PEPCK) in gooseberry (Ribes grossularia L.).

Summary Changes in carbohydrate and organic acid contents, and the occurrence and potential role of phosphoenolpyruvate carboxykinase (PEPCK) were investigated in gooseberry fruit (Ribes grossularia L., cv. White Smith), in 2006, in central Italy. The concentrations of glucose, fructose, and sucrose (mg g−1 FW) were relatively low up to 60 d after full bloom (DAFB), with glucose and fructose levels being higher than that of sucrose. All then increased up to harvest (approx. 110 DAFB), and sucrose became the most abundant soluble sugar. Malate and citrate concentrations (mg g−1 FW) and contents per fruit (mg fruit−1) increased up to 70 – 80 DAFB (malate up to approx. 70 DAFB and citrate up to approx. 80 DAFB) then decreased. The level of PEPCK was determined using both western blotting and enzyme activity measurements. PEPCK increased during fruit ripening and was most abundant when the malate and citrate contents decreased. The results are consistent with PEPCK playing a role in the catabolism of malate and citrate in gooseberry flesh during ripening.

Development and metabolism of the fruit and seed of the Japanese plum Ozark premier (Rosaceae).

The growth characteristics of some plums and their component parts have been previously studied, as have some aspects of their developmental anatomy and composition. However, little is known about either their metabolism or about the interactions between the metabolism of their component parts. In this study we investigated these aspects in the Japanese plum Ozark Premier. Throughout fruit and seed development, changes in sugar and organic acid contents, protein composition and abundance of selected enzymes were determined. In the stone, there was a transient accumulation of vegetative storage proteins. These were subsequently mobilized and this coincided with the onset of the lignification of the stone and the start of storage protein accumulation in the seed. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was present in the seeds, even though they lacked chlorophyll, and its presence may be related to limited gas exchange. In the flesh of some fruits, phosphoenolpyruvate carboxykinase (PEPCK) and NADP malic enzyme (NADP-ME) are thought to function in the dissimilation of malate and/or citrate during ripening. However, PEPCK and NADP-ME were present in plum flesh for most of its development, although there was no net dissimilation of malate until the latter stages of ripening. There is an interaction between the developing seed and endocarp with respect to the utilization of imported sugars and amino acids. An hypothesis is presented to account for the presence of PEPCK and NADP-ME enzyme in plum flesh when there was no net dissimilation of organic acids.

The occurrence of phosphoenolpyruvate carboxykinase (PEPCK) and enzymes related to photosynthesis and organic acid/nitrogen metabolism in apricot flowers (Prunus armeniaca L.)

This study determined the occurrence of phosphoenolpyruvate carboxykinase (PEPCK) and some enzymes involved in photosynthesis and organic acid/nitrogen metabolism in the different parts of apricot flowers and some other tissues of apricot. Both PEPCK protein and activity were detected in the petal, carpel, stamen filament and in the flesh of both unripe and ripe fruits, but not in the sepal or mature leaf. Both PEPCK polypeptide and activity were most abundant in the flesh of ripe fruits. In floral tissues the photosynthetic enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and putative plastidic glutamine synthase and plastidic aldolase were most abundant in the sepal in which PEPCK was not detected. The potential functions of PEPCK in the different tissues of apricot are discussed. This study highlights the potential importance of gluconeogenesis in floral metabolism.