Submitted to: Phyton International Journal Of Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/1/2001
Publication Date: N/A
Citation: Interpretive Summary: The enzyme invertase cleaves sucrose to simple sugars prior to its utilization in crop plants. Scientists at the Center for Medical, Agricultural, & Veterinary Entomology in the Crop Genetics & Environmental Research Unit (CGERU)in Gainesville, FL, have shown previously that the lack of this activity in certain mutant genotypes in maize leads to severe loss of crop productivity. The goal our current research is to describe and understand various factors that regulate the expression of the gene, Incw1, that codes for invertase activity in plant cells. The research reported here was done at CGERU by a visiting scientist from Slovenia (and the senior author of the paper). Our results show that calcium in the culture medium has profound effects on the expression of the Incw1 gene. In particular, removal of calcium from culture medium leads to an increase in the cell wall invertase RNA, protein and the enzyme activity. These data will be useful towards a better understanding of metabolic and environmental controls of invertase activity in plants.
Technical Abstract: The cell wall-bound form of invertase (EC 18.104.22.168) from a maize cell suspension culture was affected by removal of extracellular calcium, over time, at RNA, protein and enzyme activity level. The increase in enzyme activity was detected in cells treated with 5 mM EGTA, which preferentially chelates extracellular Ca2+. Although the enzyme activity of EGTA-treated cells was low and similar to the control after 24 hours of incubation, it started to increase soon thereafter. It reached the maximum after 96 hours, when a decline of invertase activity had already been detected in the control samples. The amount of the invertase protein corresponds to its determined specific activity. Calcium depletion also induced Incw1 mRNA accumulation, and the concentration of Incw1 mRNA in EGTA-treated cells was 1.7 times higher than in the control after the first 24 hours. It remained high in the next 24 hours and slowly decreased throughout a 96 hour-incubation. At the end of the experiment the transcript level decreased and reached that of the control. The possible association of the cell wall invertase with the cell wall-bound calcium is discussed.