Characterization of a strong green tissue-specific motif in rice photosystem I gene promoter Ppsak

Abstract

Characterization of green tissue-specific promoters helps facilitate genetic improvement in crops. Here, we isolated a novel green tissue-specific expression gene Psak encoding photosystem I protein in rice through RT-PCR analysis. The 5′ flanking region from −635 to +60 (transcription start site of Psak as +1) covering parts of Psak gene and its promoter Ppsak was identified as be critical for green tissue-specific expression (including leaves and stems) in rice. Further promoter deletion analyses demonstrated that the promoter region from −559 to −232 was necessary and sufficient for green tissue-specific expression of Psak gene. Histochemical assays showed that the GUS expression of this 267-bp region was highly presented in leaves and stems, but reduced or absent in other tissues examined. The GUS expression level of this core promoter region could be 14.6- to 21.6-fold higher than that of the full-length region of Ppsak promoter in leaves and stems. These results combined with cis-acting elements prediction in Ppsak promoter suggested that the TCT motif located in this promoter played a key role in strong green tissue-specific expression.