SacRALF1, a peptide signal from the grass sugarcane (Saccharum spp.), is potentially involved in the regulation of tissue expansion.
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 microM. 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.
Departamento de Genética, Escola Superior de Agricultura Luiz de Queiroz, Universidade de São Paulo, C.P. 83, Piracicaba, SP, Brazil.
Fabiana B
FB
Mingossi
Juliana L
JL
Matos
Ana Paula
AP
Rizzato
Ane H
AH
Medeiros
Maria C
MC
Falco
Marcio C
MC
Silva-Filho
Daniel S
DS
Moura
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D018546:Hypocotyl / Q000187:drug effects / Q000254:growth & development; D008969:Molecular Sequence Data; D036361:Peptide Hormones / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D031786:Saccharum / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D036361:Peptide Hormones; D010940:Plant Proteins