The NAC transcription factor family in maritime pine (Pinus Pinaster): molecular regulation of two genes involved in stress responses.
BACKGROUND
NAC transcription factors comprise a large plant-specific gene family involved in the regulation of diverse biological processes. Despite the growing number of studies on NAC transcription factors in various species, little information is available about this family in conifers. The goal of this study was to identify the NAC transcription family in maritime pine (Pinus pinaster), to characterize ATAF-like genes in response to various stresses and to study their molecular regulation.


METHODS
We have isolated two maritime pine NAC genes and using a transient expression assay in N. benthamiana leaves estudied the promoter jasmonate response.


RESULTS
In this study, we identified 37 NAC genes from maritime pine and classified them into six main subfamilies. The largest group includes 12 sequences corresponding to stress-related genes. Two of these NAC genes, PpNAC2 and PpNAC3, were isolated and their expression profiles were examined at various developmental stages and in response to various types of stress. The expression of both genes was strongly induced by methyl jasmonate (MeJA), mechanical wounding, and high salinity. The promoter regions of these genes were shown to contain cis-elements involved in the stress response and plant hormonal regulation, including E-boxes, which are commonly found in the promoters of genes that respond to jasmonate, and binding sites for bHLH proteins. Using a transient expression assay in N. benthamiana leaves, we found that the promoter of PpNAC3 was rapidly induced upon MeJA treatment, while this response disappeared in plants in which the transcription factor NbbHLH2 was silenced.


CONCLUSIONS
Our results suggest that PpNAC2 and PpNAC3 encode stress-responsive NAC transcription factors involved in the jasmonate response in pine. Furthermore, these data also suggest that the jasmonate signaling pathway is conserved between angiosperms and gymnosperms. These findings may be useful for engineering stress tolerance in pine via biotechnological approaches.
Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Campus Universitario de Teatinos, Universidad de Málaga, 29071, Málaga, Spain. bpascual@uma.es.
Ma Belén
MB
Pascual
Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Campus Universitario de Teatinos, Universidad de Málaga, 29071, Málaga, Spain. canovas@uma.es.
Francisco M
FM
Cánovas
Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Campus Universitario de Teatinos, Universidad de Málaga, 29071, Málaga, Spain. cavila@uma.es.
Concepción
C
Ávila
D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D005810:Multigene Family; D009928:Organ Specificity / Q000235:genetics; D010802:Phylogeny; D028223:Pinus / Q000235:genetics* / Q000502:physiology*; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D013312:Stress, Physiological / Q000235:genetics*; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*
D010937:Plant Growth Regulators; D010940:Plant Proteins; D014157:Transcription Factors