Title page for ETD etd-10142005-135755
|Type of Document
||Expression of 3-hydroxy-3-methylglutaryl coenzyme a reductase in maize as influenced by light and bleaching herbicides
|Kushad, Mosbah M.
|Cramer, Carole L.
|Hatzios, Kriton K.
|Hess, John L.
|Orcutt, David M.
|Date of Defense
The activity of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A
reductase (HMGR, EC 188.8.131.52) is highly expressed in 4-day-old etiolated
seedlings of normal ('DeKalb XL72AA'), dwarf (d5), and albino
(7w3) 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 HMGR activity.
The activity of HMGR extracted from leaf tips of normal, dwarf,
and albino maize seedlings was regulated by light. HMGR activity from
leaf tips of 4-day-old maize seedlings was inhibited significantly
following exposure to strong light (600 μol/m2/s) for more than 10 h.
In contrast, HMGR activity from leaf bases and root tips of maize was
not inhibited by exposure to strong light. These results suggest that
HMGR may play an important role in cell division and that light may
regulate HMGR activity indirectly by increasing cell differentiation.
Under conditions of strong light pretreatment with the bleaching herbicides
clomazone, norflurazon, fluridone and acifluorfen stimulated
by 4-to 7-fold the activity of HMGR extracted from 'Dekalb XL72AA' maize seedlings.
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