DNA-SEQUENCE ANALYSIS OF A CYCLOPHILIN GENE FROM MAIZE - DEVELOPMENTAL EXPRESSION AND REGULATION BY SALICYLIC-ACID

In plants, such as maize, cyclophilin (Cyp) genes are expressed at a b asal level in all tissues. Amounts of Cyp mRNA above the basic level a re observed in germinating seedlings, in growing tissues/organs such a s roots and leaf meristematic tissue of young maize plants, nodes and embryonic female inflorescences of adult plants and also in non-prolif erating tissues such as the internodes of adult plants. Salicylic acid (SA) enhances the transcription of maize Cyp genes. The possible invo lvement of SA in the pathway leading to defense responses induced by a biotic stresses such as mercuric chloride treatment is discussed. A ma ize Cyp genomic clone isolated using a maize Cyp cDNA probe contains 7 37 bp of the 5' upstream and the entire coding region. This Cyp gene i s not interrupted by intervening sequences. In the 5' upstream region, characteristic transcription signals as well as putative regulatory s equences were identified. Two TATA boxes are found at positions -56 bp and -66 bp with respect to the transcription start site. Two putative heat shock elements were identified in the promoter region; a metal r egulatory element and a third heat shock element were localized in the 5' untranslated leader. Several putative polyadenylation signals and (G)T-rich sequence motifs were identified in the 3' untranslated regio n.