SacRALF1, a peptide signal from the grass sugarcane (Saccharum spp.), is potentially involved in the regulation of tissue expansion
- 338 Downloads
Rapid alkalinization factor (RALF) is part of a growing family of small peptides with hormone characteristics in plants. Initially isolated from leaves of tobacco plants, RALF peptides can be found throughout the plant kingdom and they are expressed ubiquitously in plants. We took advantage of the small gene family size of RALF genes in sugarcane and the ordered cellular growth of the grass sugarcane leaves to gain information about the function of RALF peptides in plants. Here we report the isolation of two RALF peptides from leaves of sugarcane plants using the alkalinization assay. SacRALF1 was the most abundant and, when added to culture media, inhibited growth of microcalli derived from cell suspension cultures at concentrations as low as 0.1 μM. Microcalli exposed to exogenous SacRALF1 for 5 days showed a reduced number of elongated cells. Only four copies of SacRALF genes were found in sugarcane plants. All four SacRALF genes are highly expressed in young and expanding leaves and show a low or undetectable level of expression in expanded leaves. In half-emerged leaf blades, SacRALF transcripts were found at high levels at the basal portion of the leaf and at low levels at the apical portion. Gene expression analyzes localize SacRALF genes in elongation zones of roots and leaves. Mature leaves, which are devoid of expanding cells, do not show considerable expression of SacRALF genes. Our findings are consistent with SacRALF genes playing a role in plant development potentially regulating tissue expansion.
KeywordsAlkalinization assay Cell suspension Development Peptide hormone
The authors thank Gregory Pearce (Washington State University, Pullman, WA) for helpful discussions on peptide purification. Prof. Antonio Figueira (CENA/USP, Piracicaba, Brazil) for Real-time PCR facilities. Dr. Kathy Stone and Dr. Tom Abbott from the Yale Cancer Center Mass Spectrometry Resource and W. M. Keck Foundation Biotechnology Resource Laboratory Keck facility for LC MS/MS analysis. This research was supported by Fundação de Amparo a Pesquisa do Estado de São Paulo, FAPESP projects 02/08661-1, 08/11109-5 and the Bioenergy Program (08/52067-3)- BIOEN. F.B.M. was supported by graduate fellowship from CAPES. J.L.M., A.P.R. and A.H.M. were supported by fellowships from FAPESP. M.C.S.F. is a research fellow of CNPq. D.S.M. is recipient of a Young Researcher Grant from FAPESP.
- Dickison WC (2000) Integrative plant anatomy. Academic Press, New YorkGoogle Scholar
- Falco MC, Tulmann Neto A, Mendes BMJ, Zapata-Arias FJ (1996) Isolation and cultivation of sugarcane protoplasts. Braz J Plant Physiol 8:175–179Google Scholar
- Moore PH (1987) Anatomy and morphology. In: Heinz DJ (ed) Sugarcane improvement through breeding. Elsevier Science, New York, pp 85–143Google Scholar
- Vettore AL, da Silva FR, Kemper EL, Souza GM, da Silva AM, Ferro MI, Henrique-Silva F, Giglioti EA, Lemos MV, Coutinho LL, Nobrega MP, Carrer H, França SC, Bacci Júnior M, Goldman MH, Gomes SL, Nunes LR, Camargo LE, Siqueira WJ, Van Sluys MA, Thiemann OH, Kuramae EE, Santelli RV, Marino CL, Targon ML, Ferro JA, Silveira HC, Marini DC, Lemos EG, Monteiro-Vitorello CB, Tambor JH, Carraro DM, Roberto PG, Martins VG, Goldman GH, de Oliveira RC, Truffi D, Colombo CA, Rossi M, de Araujo PG, Sculaccio SA, Angella A, Lima MM, de Rosa Júnior VE, Siviero F, Coscrato VE, Machado MA, Grivet L, Di Mauro SM, Nobrega FG, Menck CF, Braga MD, Telles GP, Cara FA, Pedrosa G, Meidanis J, Arruda P (2003) Analysis and functional annotation of an expressed sequence tag collection for tropical crop sugarcane. Genome Res 13:2725–2735CrossRefPubMedGoogle Scholar
- Weigel D, Glazebrook J (2002) Arabidopsis: a laboratory manual. Cold Spring Harbor Laboratory Press, Cold Spring HarborGoogle Scholar