ZmES genes encode peptides with structural homology to defensins and are specifically expressed in the female gametophyte of maize.
All four members of a gene family, which are highly expressed in the cells of the female gametophyte (ZmES1--4: Zea mays embryo sac), were isolated from a cDNA library of maize egg cells. High expression of ZmES genes in the synergids around the micropylar region was detected in thin sections of maize ovaries. Single-cell RT--PCR analyses with the various cells of the female gametophyte confirmed the expression in synergids and also showed expression in the egg cell and central cell, and low expression in the antipodals. The expression of the whole gene family is suppressed after fertilization of the embryo sac, and expression in two-cell or later embryo stages or other tissues of maize could not be detected. In order to investigate ZmES mRNA gradients in the highly polarized and vacuolized cells of the maize embryo sac, a whole-mount in situ protocol with isolated single cells was developed: as for total RNA, ZmES transcripts are uniformly distributed in the cytoplasm of egg cell, synergids and central cell. ZmES genes encode small, cysteine-rich proteins with an N-terminal signal peptide, probably for translocation into the embryo sac cell wall. The four ZmES proteins display high sequence identity with each other, and the proposed tertiary structure of the mature peptides is similar to that of plant and animal defensins. The function of ZmES1-4 during the fertilization process is discussed.
Cordts
S
S
Applied Plant Molecular Biology II, University of Hamburg, Ohnhorststrasse 18, D-22609 Hamburg, Germany.
Bantin
J
J
Wittich
P E
PE
Kranz
E
E
Lörz
H
H
Dresselhaus
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003545:Cysteine; D023082:Defensins / Q000737:chemistry / Q000235:genetics; D015723:Gene Library; D017343:Genes, Plant; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D005810:Multigene Family; D016366:Open Reading Frames; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000502:physiology / Q000648:ultrastructure; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D003313:Zea mays / Q000235:genetics* / Q000502:physiology
D023082:Defensins; D010940:Plant Proteins; C427729:ZmES protein, Zea mays; D003545:Cysteine