Figure 9.

NMT1 and NMT3 redundantly control ovule and female gametophyte development through nontotally penetrant functions. A to F, Mature ovules, FG7 stage: the wild type (A), nmt1 (B), nmt3 (C), and nmt1 nmt3 (D–F). nmt1 nmt3 ovules with fully enclosing integuments were rare (at most one in 10 to 20 of the several hundred ovules examined, across multiple siliques). . G and J, MMC of wild-type (G) and nmt1 nmt3 (J) ovules. H and K, Tetrad of haploid megaspores in wild-type (H) and nmt1 nmt3 (K) ovules. I and L, Female gametophyte in the wild type (I) and nmt1 nmt3 (L) at stage FG1. The arrowhead in I points to the functional megaspore. No megaspore has been retained in L, as in the vast majority (at least 90%) of the ovules examined that developed normally up to that stage. In A to F, dashed lines highlight the contours of the four-celled embryo sac (A–C), an abnormal structure within the nucellus of nmt1 nmt3 ovules (D and E), and an abnormally patterned and incompletely enclosed nmt1 nmt3 ovule (F). In H and K, dashed lines highlight the megaspore tetrad in wild-type (H) and nmt1 nmt3 (K) ovules. Bars = 25 nm.