Abstract
Plants represent the heteromorphic life cycle consisting of haploid gametophyte and diploid sporophyte generations. Toward understanding the regulatory mechanisms of this life cycle, we analyze transcriptional regulatory mechanisms of sporophyte- and gametophyte-specific genes in the red alga Porphyra yezoensis. We first identified two Na+-ATPase (Na+ pump) genes, designated PyATP1A and PyATP1B. Results of RT-PCR indicated that the former is dominantly expressed in sporophytes, whereas expression of the latter is gamrtophyte-specific. We next focused on analysis of the mechanism regulating sporophyte-dominant expression of PyATP1A by the particle bombardment method for which a gene encoding PyGUS, a codon-modified β-gulucronidase (GUS), was used as a reporter. The results of 5'deletion analyses represented existence of a gametophyte-specific negative regulatory region in the PyATP1A promoter, suggesting that gametophyte-specific repression is responsible for the sporophyte-dominant expression of the PyATP1A. We are now trying to identify the negative cis-regulatory element in the PyATP1A promoter and to elucidate the mechanism of gametophyte-specific expression of PyATP1B.
