JXB Advance Access originally published online on February 27, 2004
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Journal of Experimental Botany, Vol. 55, No. 398, pp. 951-953, April 1, 2004
© 2004 Oxford University Press
GENE NOTE |
Regulated expression of a novel TCP domain transcription factor indicates an involvement in the control of meristem activation processes in Solanum tuberosum
Received 11 August 2003; Accepted 3 December 2003
Quality, Health and Nutrition, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
* To whom correspondence should be addressed. Fax: +44 (0)1382 562426. E-mail:mtaylo{at}scri.sari.ac.uk
 |
Abstract |
|---|
 Top Abstract References |
|---|
In this study, the aim was to determine whether TCP transcription factors are implicated in meristem activation in potato (Solanum tuberosum). By searching a database of potato EST sequences, with a sequence characteristically conserved in TCP domains, a potato tcp gene was identified. A BAC clone containing the tcp sequence was isolated and the genomic sequence was determined. Using a CAPS marker assay, the potato tcp gene (sttcp1) was mapped to chromosome 8. In dormant buds, relatively high levels of sttcp1-specific transcript were detected by in situ hybridization. By contrast, in sprouting buds, no expression of the sttcp1 could be detected. Furthermore, an inverse relationship between axillary bud size and the steady-state level of the sstcp1 transcript was demonstrated. In non-growing buds exhibiting correlative inhibition, sttcpI-specific transcript levels were also relatively high, but rapidly decreased when apical dominance was removed by excision of the apical bud.
Key words: In situ hybridization, meristem activation, potato, regulation, Solanum tuberosum, tcp gene, transcription factors.
|
|
TopAbstractReferences |
|---|
The recently defined TCP family of transcription factors (Cubas et al., 1999) are implicated in processes related to cell proliferation (Doebley et al., 1995; Cubas et al., 1999; Luo et al., 1996). It appears that TCP domain proteins have been recruited during evolution to control cell division and growth in various developmental processes. The objective of this study was to determine whether potato ESTs containing a characteristic TCP bHLH domain could be identified and to examine the expression pattern of the potato TCP gene in axillary and apical meristems during dormancy release.
A BLAST search (Altschul et al., 1990) of the potato gene index sequences (at http://ftp.tigr.org/tdb/potato) was carried out using the consensus sequence of the bHLH domains of previously identified plant genes (Cubas et al., 1999). One potato EST (GenBank accession number AW906880 [GenBank] ) derived from axillary buds of stem explants, was identified as containing this domain. PCR primers, based on the AW906880 [GenBank] sequence, were used to isolate a potato BAC clone (sttcpI). Four positive clones were identified from screening 3.5 genome equivalents, indicative of a single copy gene. A 12 kb HindIII sub-clone was partially sequenced to provide all the protein encoding sequence, 3238 bp of 5' upstream sequence and 2250 bp of sequence from the 3' terminus of the gene (EMBL accession number AJ561196).
An open reading frame identified in the sttcp1 sequence extends from nucleotide 3239 to 4259 and encodes a polypeptide of relative molecular mass 38 200 and isoelectric point 7.2. Comparison of the deduced amino acid sequence revealed the presence of two domains that are highly conserved in the TCP family of transcription factors, the bHLH domain and the R-domain (Cubas et al., 1999; Fig. 1A, B).
|
Using a CAPS marker assay (an A/G polymorphism in a HinfI restriction site at nucleotide 3208 in the sttcp1 sequence), and the PDH538xIVP48 diploid mapping population (Bryan et al., 2002), it was demonstrated that sttcp1 maps to potato chromosome VIII.
The expression pattern of sttcpI was determined in potato tuber apical buds and adjacent tissues during the dormancy breaking period by in situ hybridization. An antisense probe for the sttcp1 gene was synthesized using a fragment of the sttcp1 gene from bases 3516 to 3029 (containing only coding sequence) as template. Relatively high levels of transcript were detected in sections from dormant tubers. In these tubers, sttcpI was highly expressed in cells within both apical and axillary meristems (Fig. 2A, B) and was found in both the tunica and corpus of the apical meristem, especially in the peripheral zones. Transcript was also detected in procambial and early vascular tissue, both subtending the meristem, and in adjacent leaf primordia. Transcript was not detected in either ground or dermal tissues. Control samples from dormant tubers (Fig. 2C) were hybridized to sense probes and showed no blue coloration in any region of the meristem, or in leaf primordia, scale leaves, or subtending tuber tissue indicating an absence of sttcp1 expression. In sprouting buds that were stored for 8–10 weeks at 4 °C, visible growth of the bud had occurred (Fig. 2E). In these buds, probed with either antisense (Fig. 2E, F) or sense probes (Fig. 2D) no expression of sttcp1 could be detected in any tissue. Very low levels of background staining were detected in nuclei (see Fig. 2F, arrows), but no cytoplasmic signal was present.
|
The steady-state level of the sttcpI-specific transcript was determined by RT-PCR in potato buds from a range of physiological conditions in order to investigate any correlation with bud growth. In dormant potato tuber apical buds, the expression level was 6.3-fold higher than in buds that had been stored at 4 °C for 6 weeks and which were in the early stages of sprouting (assessed by visible growth of the apical bud, Fig. 3). Potato tubers that had been stored for 6–8 months at 4 °C produced a single, long, etiolated sprout, which developed from the tuber apical meristem. Due to apical dominance, other buds on the sprout are repressed. RNA was extracted from the apical 1 mm of the apical bud and from the first, fifth, and tenth buds. The sttcp1 steady-state expression level was determined by RT-PCR and the smallest buds found to have the highest expression levels.
|
In additional experiments, the growth of buds in excised sprout segments was determined over a 72 h period as described by Chatfield et al. (2000). Growth of excised buds was measurable after 12 h and growth rate increased to 6 mm d–1 between 48 h and 72 h. By contrast, growth of buds from the same nodes of intact plants was not detectable on this timescale. Total RNA was extracted from the apical 1 mm of excised buds and was analysed for sttcp1 transcript level by RT-PCR. During the first 24 h following excision there was a marked decrease in steady-state level (estimated by densitometry to be a 10.4-fold decrease, Fig. 3).
In the apical 5 mm of stolon tips or in tuber apical buds from developing tubers sttcp1 expression level increased as tuberization progressed (Fig. 3) and was 2.8-fold higher in the apical buds of developing tubers of 20 g FW than in non-tuberizing stolon tips.
In conclusion, the expression of sttcp1 correlates with meristem inactivity both in apical and axillary meristems in potato. This may suggest that sttcp1 has a function similar to that of the maize tb1 gene and may also indicate common mechanisms in the control of both apical meristem and axillary meristem activation.
|
Acknowledgements |
|---|
This work was funded by the Scottish Executive Environment and Rural Affairs Department. OFR is grateful to the EU for her post-doctoral Marie Curie fellowship.
|
References |
|---|
|
TopAbstractReferences |
|---|
Altschul SF, Gish W, Miller W, Myers EW, Lipman D. 1990. Basic and local alignment search tool. Journal of Molecular Biology 215, 403–410.[CrossRef][Web of Science][Medline]
Bryan GJ, McLean K, Bradshaw JE, Phillips M, Castelli L, De Jong WS, Waugh R. 2002. Mapping QTL for resistance to the cyst nematode Globodera pallida derived from the wild potato species Solanum vernei. Theoretical and Applied Genetics 105, 68–77.[CrossRef][Web of Science][Medline]
Chatfield SP, Stirnberg P, Forde BG, Leyser O. 2000. The hormonal regulation of axillary bud growth in Arabidopsis. The Plant Journal 24, 159–169.[CrossRef][Web of Science][Medline]
Cubas P, Lauter N, Doebley J, Coen E. 1999. The TCP domain: a motif found in proteins regulating plant growth and development. The Plant Journal 18, 215–222.[CrossRef][Web of Science][Medline]
Doebley J, Stec A, Gustus C. 1995. Teosinte branched1 and the origin of maize: evidence for epistasis and the evolution of dominance. Genetics 141, 333–346.[Abstract]
Luo D, Carpenter R, Vincent C, Copsey L, Coen E. 1996. Origin of floral asymmetry in Antirrhinum. Nature 383, 794–799.[CrossRef][Medline]
Simpson CG, Clark G, Davidson D, Smith P, Brown JWS. 1996. Mutation of putative branchpoint consensus sequences in plant introns reduces splicing efficiency. The Plant Journal 9, 369–380.[CrossRef][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  C. Damerval, M. L. Guilloux, M. Jager, and C. Charon Diversity and Evolution of CYCLOIDEA-Like TCP Genes in Relation to Flower Development in Papaveraceae Plant Physiology, February 1, 2007; 143(2): 759 - 772. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Destefano-Beltran, D. Knauber, L. Huckle, and J. Suttle Chemically forced dormancy termination mimics natural dormancy progression in potato tuber meristems by reducing ABA content and modifying expression of genes involved in regulating ABA synthesis and metabolism J. Exp. Bot., August 1, 2006; 57(11): 2879 - 2886. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. H. Kebrom, B. L. Burson, and S. A. Finlayson Phytochrome B Represses Teosinte Branched1 Expression and Induces Sorghum Axillary Bud Outgrowth in Response to Light Signals Plant Physiology, March 1, 2006; 140(3): 1109 - 1117. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||