Biology Reference
In-Depth Information
Table 1
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Continued
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Targeted Reverse Genetic Approaches Identified Female
Gametophytic and Zygotic Mutants
Initial examination of our dataset for previously characterized genes revealed that
the dataset contained 33 genes that were reported to be essential for female game-
tophyte or seed development (Figure 3). Given the availability of T-DNA mutants
from the Arabidopsis stock centers, we wished to examine T-DNA knockout lines
of some selected embryo sac expressed genes for ovule or seed abortion. During
the first phase of our screen using 90 knockout lines, we identified eight semi-
sterile mutants with about 50% infertile ovules indicating gametophytic lethal-
ity, and four mutants with about 25% seed abortion suggesting zygotic lethality
(Table 2). When we examined the mutant ovules of gametophytic mutants, we
found that seven mutants exhibited a very similar terminal phenotype: an arrested
one-nucleate embryo sac. Co-segregation analysis by phenotyping and genotyp-
ing of one such mutant, namely frigg (fig-1) demonstrated that the mutant was
not tagged, and the phenotype caused by a possible reciprocal translocation that
may have arisen during T-DNA mutagenesis (Table 2). Preliminary data suggest-
ed that the six other mutants with a similar phenotype were not linked to the gene
disruption either. Although not conclusively shown, it is likely that these mu-
tants carry a similar translocation and, therefore, we did not analyze them further.
These findings demonstrate that among the T-DNA insertation lines available, a
rather high percentage (7/90 [8%]) exhibit a semisterile phenotype that is not due
to the insertion. Therefore, caution must be exercised in screens for gametophytic
mutants among these lines.
