The Arabidopsis GAMYB-like genes, MYB33 and MYB65, are microRNA-regulated genes that redundantly facilitate anther development.
The functions of the vast majority of genes encoding R2R3 MYB domain proteins remain unknown. The closely related MYB33 and MYB65 genes of Arabidopsis thaliana have high sequence similarity to the barley (Hordeum vulgare) GAMYB gene. T-DNA insertional mutants were isolated for both genes, and a myb33 myb65 double mutant was defective in anther development. In myb33 myb65 anthers, the tapetum undergoes hypertrophy at the pollen mother cell stage, resulting in premeiotic abortion of pollen development. However, myb33 myb65 sterility was conditional, where fertility increased both under higher light or lower temperature conditions. Thus, MYB33/MYB65 facilitate, but are not essential for, anther development. Neither single mutant displayed a phenotype, implying that MYB33 and MYB65 are functionally redundant. Consistent with functional redundancy, promoter-beta-glucuronidase (GUS) fusions of MYB33 and MYB65 gave identical expression patterns in flowers (sepals, style, receptacle, anther filaments, and connective but not in anthers themselves), shoot apices, and root tips. By contrast, expression of a MYB33:GUS translational fusion in flowers was solely in young anthers (consistent with the male sterile phenotype), and no staining was seen in shoot meristems or root tips. A microRNA target sequence is present in the MYB genes, and mutating this sequence in the MYB33:GUS fusion results in an expanded expression pattern, in tissues similar to that observed in the promoter-GUS lines, implying that the microRNA target sequence is restricting MYB33 expression. Arabidopsis transformed with MYB33 containing the mutated microRNA target had dramatic pleiotrophic developmental defects, suggesting that restricting MYB33 expression, especially in the shoot apices, is essential for proper plant development.
Millar
Anthony A
AA
Commonwealth Scientific and Industrial Research Organization, Division of Plant Industry, Canberra ACT 2601, Australia. tony.millar@csiro.au
Gubler
Frank
F
D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008027:Light; D035683:MicroRNAs / Q000235:genetics; D008957:Models, Genetic; D016254:Mutagenesis, Insertional; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D013696:Temperature
D004269:DNA, Bacterial; D018744:DNA, Plant; D035683:MicroRNAs; D018749:RNA, Plant; C036483:T-DNA
Nature. 2000 Dec 14;408(6814):796-815
11130711
Plant J. 1998 Dec;16(6):735-43
10069079
Plant Cell. 1993 Dec;5(12):1739-1748
12271054
Curr Biol. 2003 Sep 2;13(17):1524-30
12956955
Curr Opin Plant Biol. 2004 Feb;7(1):65-72
14732443
Plant J. 1999 Mar;17(6):699-707
10230066
Nature. 1995 Oct 12;377(6549):495-500
7566146
Nature. 2003 Sep 18;425(6955):257-63
12931144
Plant J. 2003 Feb;33(3):481-91
12581306
Plant Physiol. 1995 Oct;109(2):697-706
12228623
Curr Opin Plant Biol. 2001 Oct;4(5):447-56
11597504
Plant Cell. 1995 Nov;7(11):1879-91
8535141
Plant Cell. 1992 Feb;4(2):203-11
1386000
Plant Mol Biol. 1999 Nov;41(5):577-85
10645718
Curr Biol. 2003 Oct 14;13(20):1768-74
14561401
Plant Cell. 1998 Oct;10(10):1585-602
9761788
Plant Mol Biol. 1994 Sep;25(6):989-94
7919218
Plant Physiol. 1999 Apr;119(4):1271-8
10198085
Plant Cell. 1990 Aug;2(8):755-67
2152125
Plant Cell. 2004 Jan;16(1):33-44
14688295
Plant J. 1999 Jan;17(1):1-9
10069063
Plant Physiol. 1991 Sep;97(1):409-14
16668400
Cell. 2002 Jul 26;110(2):261-71
12150933
Plant Physiol. 2001 Aug;126(4):1738-53
11500571
Plant J. 2002 Feb;29(4):453-64
11846878
Plant Cell. 1999 Dec;11(12):2283-90
10590158
Cell. 2002 Aug 23;110(4):513-20
12202040
Plant J. 2002 Mar;29(5):581-94
11874571
Proc Natl Acad Sci U S A. 1991 Aug 15;88(16):7266-70
1831269
Development. 2004 Jul;131(14):3357-65
15226253
Planta. 1998 Aug;205(4):492-505
9684354
Plant Cell. 1992 Nov;4(11):1435-41
1477556
Curr Biol. 2002 Sep 3;12(17):1484-95
12225663
Plant Physiol. 2001 Dec;127(4):1682-93
11743113
Proc Natl Acad Sci U S A. 2004 Jan 27;101(4):1093-8
14722360
Plant J. 1999 Jul;19(2):107-118
10476058