Temporal and spatial expression of amygdalin hydrolase and (R)-(+)-mandelonitrile lyase in black cherry seeds.

AUTOR(ES)

Zheng, L

RESUMO

In black cherry (Prunus serotina Ehrh.) macerates, the cyanogenic diglucoside (R)-amygdalin undergoes stepwise degradation to HCN catalyzed by amygdalin hydrolase (AH), prunasin hydrolase, and (R)-(+)-mandelonitrile lyase (MDL). A near full-length AH cDNA clone (pAH1), whose insert encodes the isozyme AH I, has been isolated and sequenced. AH I exhibits several features characteristic of beta-glucosidases of the BGA family, including their likely nucleophile center (isoleucine-threonine-glutamic acid-asparagine-glycine) and acid catalyst (asparagine-glutamic acid-proline/isoleucine) motifs. The temporal expression of AH and MDL in ripening fruit was analyzed by northern blotting. Neither mRNA was detectable until approximately 40 days after flowering (DAF), when embryos first became visible to the naked eye. Both mRNAs peaked at approximately 49 DAF before declining to negligible levels when the fruit matured (82 DAF). Taken together with enzyme activity data, these time courses suggest that AH and MDL expression may be under transcriptional control during fruit maturation. In situ hybridization analysis indicated that AH transcripts are restricted to the procambium, whereas MDL transcripts are localized within cotyledonary parenchyma cells. These tissue-specific distributions are consistent with the major locations of AH and MDL protein in mature seeds previously determined by immunocytochemistry (E. Swain, C.P. Li, and J.E. Poulton [1992] Plant Physiol 100:291-300).

Documentos Relacionados

• Molecular Analysis of (R)-(+)-Mandelonitrile Lyase Microheterogeneity in Black Cherry1
• Sequencing, genomic organization, and preliminary promoter analysis of a black cherry (R)-(+)-mandelonitrile lyase gene.
• Tissue Level Compartmentation of (R)-Amygdalin and Amygdalin Hydrolase Prevents Large-Scale Cyanogenesis in Undamaged Prunus Seeds.
• Purification and Characterization of a Novel (R)-Mandelonitrile Lyase from the Fern Phlebodium aureum.
• Light-Dependent Spatial and Temporal Expression of Pigment Regulatory Genes in Developing Maize Seeds.