Submitted to: Journal of Biological Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/17/2000
Publication Date: N/A
Citation: Interpretive Summary: The goal was isolate and characterize a DNA sequence that encodes an enzyme involved in the transfer of the signal leading to events induced during low oxygen conditions in maize during flooding. A DNA sequence from corn has been isolated and characterized. This sequence encodes an enzyme that appears to be involved in perception of an oxygen deficit, when a corn seedling is subjected to flooding. The perception of the oxygen deficit is mediated by calcium ions. This perception leads to molecular, physiological and morphological responses to flooding. Understanding this enzyme's role in a plant's response to low oxygen-stress conditions will allow for a greater understanding of how plants attempt to cope with this stress and may allow for effective methods to produce crop plants that are tolerant to flooding.
Technical Abstract: A cDNA (CAP1) isolated from maize roots, shares sequence identity with genes encoding P-type Ca2+-ATPases and restores the growth phenotype of yeast mutants defective in Ca2+-pumps. CAP1 was transcribed and translated in the yeast mutant. Furthermore, the membrane-integrated product formed a Ca2+-dependent phosphorylated intermediate and supported Ca2+-transport. Although CAP1 shares greater sequence identity with mammalian "ER-type" Ca2+-pumps, it differs from these genes by having features of calmodulin (CaM)-regulated Ca2+-pumps. CAP1 from yeast microsomes bound CaM and the CAP1-dependent Ca2+-transport in yeast was stimulated by CaM. Peptides from the C-terminus of CAP1 bound CaM. Anti-CAP1 antibodies specifically recognized a maize microsomal polypeptide that also bound CaM. A similar polypeptide also formed a Ca2+-dependent phosphoenzyme. Our results suggest that cap1 encodes a novel form of CaM-regulated Ca2+-ATPase in maize. CAP1 appears to be encoded by one or two genes in maize. CAP1 RNA is induced only during early anoxia, indicating that the Ca2+-pump may play an important role in O2-deprived maize cells.