TY - JOUR

T1 - An early nodulin-like protein accumulates in the sieve element plasma membrane of Arabidopsis

AU - Khan, Junaid A.

AU - Wang, Qi

AU - Sjölund, Richard D.

AU - Schulz, Alexander

AU - Thompson, Gary A.

PY - 2007

Y1 - 2007

N2 - Membrane proteins within the sieve element-companion cell complex have essential roles in the physiological functioningof the phloem. The monoclonal antibody line RS6, selected from hybridomas raised against sieve elements isolated fromCalifornia shield leaf (Streptanthus tortuosus; Brassicaceae) tissue cultures, recognizes an antigen in the Arabidopsis (Arabidopsisthaliana) ecotype Columbia that is associated specifically with the plasma membrane of sieve elements, but not companioncells, and accumulates at the earliest stages of sieve element differentiation. The identity of the RS6 antigen was revealed byreverse transcription-PCR of Arabidopsis leaf RNA using degenerate primers to be an early nodulin (ENOD)-like protein thatis encoded by the expressed gene At3g20570. Arabidopsis ENOD-like proteins are encoded by a multigene family composed ofseveral types of structurally related phytocyanins that have a similar overall domain structure of an amino-terminal signalpeptide, plastocyanin-like copper-binding domain, proline/serine-rich domain, and carboxy-terminal hydrophobic domain.The amino- and carboxy-terminal domains of the 21.5-kD sieve element-specific ENOD are posttranslationally cleaved fromthe precursor protein, resulting in a mature peptide of approximately 15 kD that is attached to the sieve element plasmamembrane via a carboxy-terminal glycosylphosphatidylinositol membrane anchor. Many of the Arabidopsis ENOD-like proteinsaccumulate in gametophytic tissues, whereas in both floral and vegetative tissues, the sieve element-specific ENOD isexpressed only within the phloem. Members of the ENOD subfamily of the cupredoxin superfamily do not appear to bindcopper and have unknown functions. Phenotypic analysis of homozygous T-DNA insertion mutants for the gene At3g20570shows minimal alteration in vegetative growth but a significant reduction in the overall reproductive potential.

AB - Membrane proteins within the sieve element-companion cell complex have essential roles in the physiological functioningof the phloem. The monoclonal antibody line RS6, selected from hybridomas raised against sieve elements isolated fromCalifornia shield leaf (Streptanthus tortuosus; Brassicaceae) tissue cultures, recognizes an antigen in the Arabidopsis (Arabidopsisthaliana) ecotype Columbia that is associated specifically with the plasma membrane of sieve elements, but not companioncells, and accumulates at the earliest stages of sieve element differentiation. The identity of the RS6 antigen was revealed byreverse transcription-PCR of Arabidopsis leaf RNA using degenerate primers to be an early nodulin (ENOD)-like protein thatis encoded by the expressed gene At3g20570. Arabidopsis ENOD-like proteins are encoded by a multigene family composed ofseveral types of structurally related phytocyanins that have a similar overall domain structure of an amino-terminal signalpeptide, plastocyanin-like copper-binding domain, proline/serine-rich domain, and carboxy-terminal hydrophobic domain.The amino- and carboxy-terminal domains of the 21.5-kD sieve element-specific ENOD are posttranslationally cleaved fromthe precursor protein, resulting in a mature peptide of approximately 15 kD that is attached to the sieve element plasmamembrane via a carboxy-terminal glycosylphosphatidylinositol membrane anchor. Many of the Arabidopsis ENOD-like proteinsaccumulate in gametophytic tissues, whereas in both floral and vegetative tissues, the sieve element-specific ENOD isexpressed only within the phloem. Members of the ENOD subfamily of the cupredoxin superfamily do not appear to bindcopper and have unknown functions. Phenotypic analysis of homozygous T-DNA insertion mutants for the gene At3g20570shows minimal alteration in vegetative growth but a significant reduction in the overall reproductive potential.

U2 - 10.1104/pp.106.092296

DO - 10.1104/pp.106.092296

M3 - Journal article

VL - 143

SP - 1576

EP - 1589

JO - Plant Physiology

JF - Plant Physiology

SN - 0032-0889

IS - 4

ER -