In the search of glutamate sources in ripe tomato fruits

SORREQUIETA, AUGUSTO, FERRARO, GISELA, MORTERA, PABLO, BOGGIO, SILVANA B., VALLE, ESTELA M.

Mérida, México

Congreso; ASPB 2008; 2008

Asociation of Plant Biology

Tomato fruits from cultivated varieties increase free glutamate content significantly during ripening (Boggio et al 2000). In this work we analyzed the expression level as well as activity of enzymes involved in glutamate metabolism in mature fruits of the cv. Micro-Tom during the ripening transition. Initially, we established that glutamate was not produced from digestion of endogenous pericarp proteins by any kind of peptidase present in the mature fruits. Activity analysis of glutamate dehydrogenase (GDH) and enzymes of the GABA shunt during fruit ripening indicated that all enzymes were active in fruits. In addition, the ratio of aminating to deaminating GDH activity and GABA transaminase (GABA-T) increased markedly in ripe fruits. From all the enzymes tested, GABA-T activity was the only one that correlated with transcript levels (one isoform). These enzyme activities and transcripts were also searched in ex-planta ripening fruits. Results showed that the patterns of enzyme induction were different to those of in-planta matured fruits. Possible metabolic routes contributing to glutamate accumulation in Micro-Tom fruits during ripening will be discussed. References Boggio et al. 2000 Plant Sci 159:125-133