Plant Genome I Conference
Town & Country Conference Center, San Diego, CA, November, 1992.
PG-I: 33pg1
PLANT NODULE-SPECIFIC GENES EXPRESSED IN EMPTY MEDICAGO
NODULES.
Rebecca Dickstein, Nita Prabhu, and Reeta Prusty, Department of
Bioscience and Biotechnology, Drexel University, Philadelphia, PA
19104.
The formation of effective nitrogen-fixing root nodules by
leguminous plants with symbiotic rhizobia soil bacteria is
accompanied by the expression of nodule-specific plant genes. In
alfalfa, the development of the nodule structure can be separated
from invasion of the nodule by bacteria we took advantage of the
observation that R. meliloti exopolysaccharide (exo) mutants
block nodule development at the empty nodule stage and identified
several nodule-specific genes expressed in empty nodules elicited
by R. meliloti exo mutants. One of the genes is the
well-characterized ENOD2 (Early NODulin 2), which encodes a
proline-rich polypeptide that is similar to extensin, and is a
putative cell wall protein. ENOD2 has been isolated as several
partial cDNAs so far. The other two cDNAs that we are studying,
11A and 12C, cross-hybridize to each other at moderate, but not
high, stringency. Interestingly, the preliminary results from
the partial sequence of one of these indicates that it does not
encode a proline-rich polypeptide in any reading frame. Thus,
this gene may not encode a putative cell wall protein. The 12C
gene is expressed at approximately the same time as ENOD2 during
the development of wild-type nodules; its expression during the
development of empty nodules is being examined. These genes are
also being investigated in the diploid, self-fertile Medicago
truncatula. We have obtained genomic clones of the 11A and 12C
genes from M. truncatula.
Return to Previous Page or Intl-PAG Homepage