Novel Anther-Specific myb Genes from Tobacco as Putative Regulators of Phenylalanine Ammonia-Lyase Expression

• Published in: Plant physiology (Bethesda) 2001-08, Vol.126 (4), p.1738-1753
• Main Authors: Seungchan Yang, Justin P. Sweetman, Sasan Amirsadeghi, Medhi Barghchi, Huttly, Alison K., Won-Il Chung, Twell, David
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Amino acids; Ammonia; Animals; Anthers; Biological and medical sciences; Cloning, Molecular; Complementary DNA; Development and Hormone Action; DNA; DNA, Complementary; DNA, Plant; Economic plant physiology; Flowering, floral biology, reproduction patterns; Fundamental and applied biological sciences. Psychology; Genes; Growth and development; Humans; Hybridization; in situ hybridization; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Multigene Family; myb gene; Nicotiana - enzymology; Nicotiana - genetics; Nicotiana tabacum; Oligonucleotides; Phenylalanine Ammonia-Lyase - genetics; Phenylalanine Ammonia-Lyase - metabolism; Phenylpropionates - metabolism; Plant physiology and development; Plant Proteins; Plant Stems; Plant tissues; Plants; Plants, Toxic; Plasmids; Pollen; Pollen - genetics; Proteins; Reproduction; Sequence Homology, Amino Acid; Sexual reproduction; Site selection; Tobacco; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription. Transcription factor. Splicing. Rna processing; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.126.4.1738

Two cDNA clones (NtmybAS1 and NtmybAS2) encoding MYB-related proteins with strong sequence similarity to petunia (Petunia hybrida) PhMYB3 were isolated from a tobacco (Nicotiana tabacum cv Samsun) pollen cDNA library. Northern blot and in situ hybridization revealed that NtmybAS transcripts are specifically expressed in both sporophytic and gametophytic tissues of the anther including tapetum, stomium, vascular tissue, and developing pollen. Random binding site selection assays revealed that NtMYBAS1 bound to DNA sequences closely resembling consensus MYB binding sites MBSI and MBSIIG, with a higher affinity for MBSI. Transient expression analyses of the N-terminal MYB domain demonstrated the presence of functional nuclear localization signals, and full-length NtMYBAS1 was able to activate two different phenylalanine ammonia-lyase promoters (PALA and gPAL1) in tobacco leaf protoplasts. Similar analysis of truncated NtmybAS1 cDNAs identified an essential, C-terminal trans-activation domain. Further in situ hybridization analyses demonstrated strict co-expression of NtmybAS and gPAL1 in the tapetum and stomium. Despite abundant expression of NtmybAS transcripts in mature pollen, gPAL1 transcripts were not detectable in pollen. Our data demonstrate that NtMYBAS1 is a functional anther-specific transcription factor, which is likely to be a positive regulator of gPAL1 expression and phenyl-propanoid synthesis in sporophytic, but not in gametophytic, tissues of the anther.