Biology Reference
In-Depth Information
To confirm the link between the small seeds and paternal inheritance of
met1-3, seeds from wt×met1-3/+ crosses were visually sorted according to their
size relative to a wild type control, and BASTA resistance associated to met1-3
was tested. Two populations of seeds were distinguished. All smallest seeds were
resistant to BASTA (n = 323) while all largest seeds were sensitive to BASTA (n =
336). The 1:1 proportion supported the predicted association of the paternal ef-
fect of met1-3 to gametogenesis (p = 0.6126
χ
2). As we did not analyze the entire
population we may have missed a complex genetic component regulating seed
size. To ensure that abnormally small seeds or seed lethality were not missing from
our bulked seed population, we analyzed all seeds from single crosses between
wild-type mothers and pollen from met1-3/+ plants (Figure 2A, Table 2). In this
analysis we also ensured that crosses with pollen from wt and met1-3/+ plants
were performed on the same mother plant to allow an absolute size comparison.
BASTA resistance correlated with the smallest seeds of the population (p<0.0001
ANOVA and Mann-Whitney) demonstrating that paternal inheritance of met1-3
causes seed size reduction as a result of the loss of MET1 activity during male
gametogenesis. The loss of MET1 during male gametogenesis may allow paternal
expression of imprinted growth inhibitors and cause a decrease of endosperm and
seed size. Loss-of-function paternal effects are uncommon and until now have
only been linked to defects in fertilization in Drosophila [18], [19], C.elegans
[20] and Arabidopsis [3]. We thus conclude that met1-3 causes a paternal effect
associated with defects after fertilization and thus representing a distinct class of
paternal effect mutations.
Figure 2.
Correlation between seed size and the inheritance of met1-3 associated to BASTA resistance.
(A) BASTA
resistance (Br) and sensitivity (Bs) are correlated with seed size in seeds from crosses between wild-
type ovules and met1-3/+ pollen. Segregation of the BASTA marker remains 1:1 (p = 0.4795
χ
2
), so although
some seed lethality was observed (n = 11) it is not linked to met1-3. (B) Br and Bs are not correlated with seed
size in seeds from crosses between met1-3/+ ovules and wild-type pollen.
