TABLE 2.
Outline description of the phenotypes of the deletion mutants and suggested function(s) of the genes involved
| Mutant class and Y deletion sizes | No. of deletion mutants | Mutant group names and possible gene functions involved in each subgroup (Roman numerals) | Phenotypic defects | Figures |
|---|---|---|---|---|
| Asexual; interstitial, up to 40% of proximal Yp | 2 | asx1, asx2 specifying primary parietal cell fate | Anther arrest before differentiation of the parietal layers, as in wild-type females. The two mutants have an identical phenotype. | 4B, S1B |
| Anther development; interstitial, up to 26% of proximal Yp | 7 | ad1–ad7 | Anthers arrested early during formation of parietal and sporogenous layers. Completely sterile. | |
| i. ad1 stamen sub-whorl coordination | Inner, antipetalous, anther subwhorl is arrested at the four-lobed stage, deposits accumulate around the connective region. Outer, antisepalous anthers form abnormally small and unviable pollen grains. | 4C, 4Q, S2K, S2L | ||
| ii. ad2, ad6 maintaining parietal layer | Anther arrest at the stage of parietal layer formation in the wild type, but microspore mother cells can undergo meiosis. The two mutants have very similar phenotype. | 4E, S1E, S1D | ||
| iii. ad3, ad5 locule synchronization | Asymmetrically developed anthers (abaxial locules form only primary parietal layers). The two mutants have an identical phenotype. | 4F, S1G, S1H | ||
| iv. ad4, ad7 specification of parietal layers | Secondary parietal layer often differentiated directly into tapetum-like cells without formation of all anther layers. The two mutants have very similar phenotype. Ad7 is altered in X–Y pairing. | 4H, S1J, S1K | ||
| Pollen fertility; interstitial, up to 8% of proximal or medial Yq | 5 | pf1–pf5 | Microspores either degenerate after meiosis, or the pollen grains are sterile. | |
| i. pf1 tapetum differentiation | Tapetum does not differentiate. | 4J, S2B | ||
| ii. pf2 tapetum/middle layer signaling | Tapetum is released from the degenerating middle layer. | 4L, S2D | ||
| iii. pf3, pf5 microspore shape | Microspores are irregular in shape. The two mutants have very similar phenotype. | 4N, S2F, S2G | ||
| iv. pf4 middle layer and tapetum degeneration function. | Tapetum and middle layer do not degenerate. | 4O, S2I |
The left-hand column lists the three major male-defective phenotypic classes and shows the total numbers of deletions found in each of them. The third column describes the general phenotype of each group (Roman numerals indicate subgroups).