Expression of 3‐hydroxy‐3‐methylglutaryl coenzyme A reductase activity in maize tissues

Abstract

The activity of the enzyme 3‐hydroxy‐3‐methlglutaryl‐coenzyme A reductase (HMGR, EC 1.1.1.34) is highly expressed in 4‐day‐old etiolated seedlings of normal (cv. DeKalb XL72AA), dwarf (d5) and albino (lw3) maize (Zea mays L.). HMGR activity of maize seedlings appeared to be exclusively associated with the microsomal rather than the plastidic fraction of maize cells. Maize tissues with high meristematic activity such as germinating seeds, leaf bases, root tips and the site of origin of lateral roots contained high levels of microsomal HMGR activity. The activity of HMGR extracted from leaf tips of normal, dwarf and albino maize seedlings is regulated by light. Microsomal HMGR activity from leaf tips of 4‐day‐old maize seedlings was inhibited significantly following exposure to strong light (600 μmol m−2 s−1) for more than 10 h. By comparison, microsomal HMGR activity from leaf bases and root tips of maize was not inhibited by exposure to strong light. These results suggest that the microsomal HMGR which is highly expressed in maize may be related to sterol biosynthesis and membrane biogenesis rather than plastidic‐associated isoprenoid synthesis and that light may regulate HMGR activity indirectly by increasing cell differentiation.

3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Activity in the Endosperm of Maize vivipary Mutants

“…It has been hypothesized that plant HMGRs may exist in specialized isozyme forms located within these different cell compartments. The existence of a plastid HMGR is controversial and unresolved at present (Gray, 1987;Bach et al, 1990); however, the available evidence in maize shows that HMGR activity is associated mainly with microsomal rather than plastid membranes (Ji et al, 1992;Moore and Oishi, ~ 1993). Thus, it seems unlikely that plastid isoform would contribute significantly to the HMGR activity during seed development.…”

“…Plant microsomal HMGR has been shown to be regulated by light (Brooker and Russell, 1979;Ji et al, 1992;Moore and Oishi, 1993), phytohormones (Brooker and Russell, 1979;Russell and Davidson, 1982), wounding, fungal infection, and fungal elicitors (Stermer and Bostock, 1987). Results from our studies of HMGR activity during seed development suggest that this enzyme and its regulation are important during seed development.…”

Ethylene and 1-Methylcyclopropene Differentially Regulate Gene Expression during Onion Sprout Suppression

“…This increase in respiration rate in response to ethylene in the presence or absence of 1-MCP may explain the increase in the expression of probes annotated as HMGR following these same treatments. In plants, HMGR may be related to sterol biosynthesis and membrane biosynthesis, and its activity has been positively correlated with rapidly dividing cells in maize (Zea mays; Ji et al, 1992). An increase in the expression of HMGR could suggest an increase in rapidly dividing cells and therefore sprout growth.…”

Seasonal Variations in Rubber Biosynthesis, 3-Hydroxy-3-Methylglutaryl-Coenzyme A Reductase, and Rubber Transferase Activities in Parthenium argentatum in the Chihuahuan Desert

“…HMGR activity in guayule stems was assayed by the procedure of Ji et al (1992). Bark was removed from the lower stems of the harvested plants, rinsed with distilled HzO, and blotted dry with paper towels.…”