Table 1.
A comprehensive list of anther mutants sequentially organized from organ specification through meiosis.
| Stage affected | A. thaliana | Rice | Maize | Annotation | Phenotype | doi |
|---|---|---|---|---|---|---|
| 1 | agamous | mads3, mads58 | Zmm2, Mads2 | MADS-box transcription factor | stamens converted to petals (Arabidopsis) or lodicules (grasses) | 10.1105/tpc.3.8.749 |
| 1 | ems71924, ems72032 | not cloned | stamen adaxialization | 10.1534/g3.112.004465 | ||
| 1 | ems71990, ms-si*355 | not cloned | absence of anthers in some florets | 10.1534/g3.112.004465 | ||
| 1 | rdr6 | rol (SHOOTLESS2) | rdr6 | RNA-directed RNA polymerase | stamen abaxialization (defect in tasi-ARF biosynthesis) | 10.1105/tpc.110.075291 |
| 2 | bam1 bam2 double mutant | LRR receptor-like kinases | all internal lobe cells become AR; no somatic cells | 10.1105/tpc.105.036871 | ||
| 2 | mil1 | msca1 | glutaredoxin | AR fail to differentiate (Os) or differentiate as vasculature (Zm) | 10.1007/s00425-002-0929-8 | |
| 2 (ad), 8 (ab) | roxy1 roxy2 double mutant | glutaredoxin (thioreductase) | adaxial lobes: AR specification failure; abaxial: PMC degrade | 10.1111/j.1365-313X.2007.03375.x | ||
| 3 | nzz = spl | no homology in grasses | MADS-box transcription factor | AR differentiation failure; somatic cell layer defects | 10.1104/pp.109.145896 | |
| 3 (Zm/Os), 5 (At) | tpd1 | tdl1a = mil2 | mac1 | small secreted protein ligand | somatic cell specification failure; overproliferation of AR | 10.1105/tpc.016618 |
| 3 | exs = ems1 | msp1 | LRR receptor-like kinase | somatic cell specification failure; overproliferation of AR | 10.1016/S0960-9822(02)01151-x | |
| 4 | ocl4 | HD-ZIP IV transcription factor | additional periclinal divisions in subepidermal cell layer | 10.1111/j.1365-313X.2009.03916.x | ||
| 4 | ems63089, tcl1, mtm00-06 | not cloned | undifferentiated somatic cell layers | 10.1534/g3.112.004465 | ||
| 5 | tip2 | bHLH transcription factor | all three anther wall layers fail to differentiate properly | 10.1105/tpc.114.123745 | ||
| 5 | er erl1 erl2 triple mutant | LRR receptor-like kinases | missing anthers and somatic cell differentiation defects | 10.1093/mp/ssn029 | ||
| 6 | tdf1 | R2R3 Myb transcription factor | early vacuolization in epidermis and endothecium, tapetal failure | 10.1111/j.1365-313X.2008.03500.x | ||
| 6 | serk1 serk2 double mutant | LRR receptor-like kinases | SPL periclinal division failure | 10.1105/tpc.105.036731 | ||
| 7 | ms23, ms*6015 | not cloned | additional periclinal divisions in the tapetal layer | 10.1534/g3.112.004465 | ||
| 7 | ems72063 | not cloned | undifferentiated soma; excess periclinal divisions in tapetum | 10.1534/g3.112.004465 | ||
| 7 | ems72091 | not cloned | additional periclinal divisions in the middle layer | 10.1534/g3.112.004465 | ||
| 7 | mpk3 and mpk6 | MAP kinases | somatic cell specification failure; overproliferation of AR | 10.1093/mp/ssn029 | ||
| 8 | dtm1 | ER membrane protein | tapetal differentiation failure | 10.1111/j.1365-313X.2011.04864.x | ||
| 8 | dyt1 | bHLH transcription factor | tapetal differentiation failure | 10.1111/j.1365-313X.2012.05104.x | ||
| 8 | myb33 myb65 double mutant | GAMYB-like transcription factor | tapetal differentiation failure | 10.1105/tpc.104.027920 | ||
| 8 | ms9, ms11, ms13, ms14 | not cloned | tapetal differentiation failure | 10.1534/g3.112.004465 | ||
| 8 | ms32 | bHLH transcription factor | excess periclinal divisions in tapetum after normal wall is built | 10.1111/tpj.12318 | ||
| 8 | csmd1 | not cloned | excess pre-meiotic callose and slow dissolution of the tetrad | 10.1007/s00497-011-0167-y | ||
| 8 | ms8 | beta-1,3-galactosyl transferase | cell growth defects in epidermis and tapetum, meiotic arrest | 10.1007/s00497-013-0230-y | ||
| 8 | gamyb-4 | GAMYB transcription factor | tapetal differentiation failure; meiotic arrest | 10.1111/j.1744-7909.2010.00959.x | ||
| meiosis | udt1 | bHLH transcription factor | tapetal differentiation failure; meiotic arrest | 10.1105/tpc.105.034090 | ||
| meiosis | mel1 | Argonaute | tapetal differentiation failure; meiotic arrest | 10.1105/tpc.107.053199 | ||
The left hand column indicates the first developmental stage at which a mutant phenotype is observed, using the staging rubric outlined in Figure 1. In cases where the onset of the phenotype differs among species or tissues, abbreviations are used (“Zm” = maize, “Os” = rice, “At” = Arabidopsis, “ab” = abaxial anther lobes, and “ad” = adaxial anther lobes). If a given mutant is phenocopied by homologs from the other two species, the gene names are given in the corresponding species' column. An exception to this rule was made for the first maize entry, “Zmm2, Mads2,” because while mutants in these genes have not been found, the genes are clearly agamous orthologs by sequence comparison and expression pattern in the third floral whorl, which is characteristic of C class genes. The next two columns contain the phenotypic description of the mutant and protein annotation if a causative gene has been cloned. Uncloned mutants are indicated as “not cloned,” and these are clustered in a single row in cases where they roughly phenocopy each other (for example, maize ems71924 and ems72032 have nearly identical anther polarity phenotypes, and may be allelic). In the final column, a doi is provided for the founding mutant of each class. The high number of blank spaces in the species' columns reflects the challenge of comparisons between model species. The bHLH, MYB, and LRR-RLK genes are all found in large families making identification of orthologs between species problematic. Furthermore, mutations in a single gene that cause a clear phenotype in one plant species may not be available in others because of functional gene redundancy from lineage specific gene duplication. And there is already evidence that orthologs can regulate different steps reflecting evolutionary diversification of developmental pathways. For these reasons we do not anticipate a high degree of correspondence between Arabidopsis, rice, and maize.