Abstract: A cDNA clone encoding a PS Ⅰ H subunit of photosystem Ⅰ from Pharbitis nil Choisy was characterized with regard to its sequence and pattern in response to light treatments. The psaH cDNA contained an open reading frame of 432 nucleotides encoding a 144 amino acid protein of approximately 16 kD which consisted of a 49 amino acid transit peptide and a 95 amino acid mature PS I H peptide. Northern analysis indicated that the expression of the psaH gene was regulated by an endogenous circadian rhythm and light was a key factor for promoting its transcription. Moreover, the level of psaH mRNA was rather different among cotyledon, stem and root of the tested seedling.

Key words: Pharbits nil, psaH cDNA clone, Endogenous circadian rhythm, Gene expression