Expression analysis of the plasma membrane H+-ATPase pma4 transcription promoter from Nicotiana plumbaginifolia activated by the CaMV 35S promoter enhancer

pma4 is the major plasma membrane H+-ATPase gene in Nicotiana plumbaginifol ia. To study its physiological role by overexpression, we evaluated the pos sibility of enhancing the pma4 transcription promoter using a 165-bp enhanc ing sequence of the CaMV 35S transcription promoter. This was inserted into the pma4 promoter either 500 or 50 nucleotides upstream from the transcrip tion start site. Transient expression with the gusA reporter gene showed th at both enhanced pma4 promoters had a 4- to 13-fold greater transcription a ctivity than the native pma4 promoter. Quantitative analysis of stable tran sgenic plants also showed that both enhanced pma4 promoters conferred much greater GUS activity. Histochemical assay showed that the enhanced promoter s produced strong GUS activity in most cell types as already observed in th e 35S or the native pma4 promoter. In the cell types where either the 35S o r pma4 promoter was inactive, the enhanced promoters mimicked expression of the active one. However, there were cases (e.g. root cortex of seedlings) where, although both 35S and pma4 promoters were active, none of the enhanc ed promoters induced GUS activity. This might indicate the interference of promoter regulatory elements. The two enhanced pma4 promoters conferred sim ilar expression throughout the plant development, implying that there was n o regulatory element at either the pma4 -500 or -50 position, that conferre d important tissue specificity. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.