Biological function of a tobacco homeobox gene,
NTH15, was studied by producing two different types of transgenic tobacco, one of which was transformed with
NTH15::GUS and the other was transformed with CaMV 35S promoter::antisense
NTH15. The GUS staining around shoot apical meristem (SAM) in transgenic plants with
NTH15::GUS revealed that the
NTH15 expression is specifically localized in the dorsal region of young leaf primordia. The transgenic plants transformed with the antisense construct lost the expression of the endogenous transcript around SAM and also showed alterations in leaf morphology. These transformants formed leaves with disorganized pinnate venation. Midribs of the malformed leaves also lost crescent-shaped vascular systems by ectopic cell vacuolization in their adaxial side. These observations suggest suppression of the
NTH15 expression around SAM causes loss of dorsoventrality in midribs. Taken together with the observations of the
NTH15 expression pattern, it may be important for the dorsoventral development of leaves that the
NTH15 gene is expressed in the adaxial side of young leaf primordia.
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