title: Lignin biosynthesis in wheat (Triticum aestivum L.): its response to waterlogging and association with hormonal levels.
abstract: BACKGROUND
  Lignin is an important structural component of plant cell wall that confers mechanical strength and tolerance against biotic and abiotic stressors; however it affects the use of biomass such as wheat straw for some industrial applications such as biofuel production. Genetic alteration of lignin quantity and quality has been considered as a viable option to overcome this problem. However, the molecular mechanisms underlying lignin formation in wheat biomass has not been studied. Combining molecular and biochemical approaches, the present study investigated the transcriptional regulation of lignin biosynthesis in two wheat cultivars with varying lodging characteristics and also in response to waterlogging. It also examined the association of lignin level in tissues with that of plant hormones implicated in the control of lignin biosynthesis.
  
  
  RESULTS
  Analysis of lignin biosynthesis in the two wheat cultivars revealed a close association of lodging resistance with internode lignin content and expression of 4-coumarate:CoA ligase1 (4CL1), p-coumarate 3-hydroxylase1 (C3H1), cinnamoyl-CoA reductase2 (CCR2), ferulate 5-hydroxylase2 (F5H2) and caffeic acid O-methyltransferase2 (COMT2), which are among the genes highly expressed in wheat tissues, implying the importance of these genes in mediating lignin deposition in wheat stem. Waterlogging of wheat plants reduced internode lignin content, and this effect is accompanied by transcriptional repression of three of the genes characterized as highly expressed in wheat internode including phenylalanine ammonia-lyase6 (PAL6), CCR2 and F5H2, and decreased activity of PAL. Expression of the other genes was, however, induced by waterlogging, suggesting their role in the synthesis of other phenylpropanoid-derived molecules with roles in stress responses. Moreover, difference in internode lignin content between cultivars or change in its level due to waterlogging is associated with the level of cytokinin.
  
  
  CONCLUSIONS
  Lodging resistance, tolerance against biotic and abiotic stresses and feedstock quality of wheat biomass are closely associated with its lignin content. Therefore, the findings of this study provide important insights into the molecular mechanisms underlying lignin formation in wheat, an important step towards the development of molecular tools that can facilitate the breeding of wheat cultivars for optimized lignin content and enhanced feedstock quality without affecting other lignin-related agronomic benefits.
authors.affiliation: Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, MB, R3T 2N2, Canada. nguyentn@myumanitoba.ca.
authors.forename: Tran-Nguyen
authors.initials: TN
authors.lastname: Nguyen
authors.affiliation: Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, MB, R3T 2N2, Canada. seung.son@umanitoba.ca.
authors.forename: SeungHyun
authors.initials: S
authors.lastname: Son
authors.affiliation: Morden Reasearch and Development Centre, Agriculture and Agri-Food Canada, Morden, MB, R6M 1Y5, Canada. mark.jordan@agr.gc.ca.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Jordan
authors.affiliation: Department of Biosystems Engineering, University of Manitoba, Winnipeg, MB, R3T 5V6, Canada. david.levin@umanitoba.ca.
authors.forename: David B
authors.initials: DB
authors.lastname: Levin
authors.affiliation: Department of Plant Science, University of Manitoba, 222 Agriculture Building, Winnipeg, MB, R3T 2N2, Canada. belay.ayele@umanitoba.ca.
authors.forename: Belay T
authors.initials: BT
authors.lastname: Ayele
mesh_terms: D018744:DNA, Plant; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008031:Lignin / Q000096:biosynthesis*; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000502:physiology*; D018547:Plant Stems / Q000378:metabolism; D018749:RNA, Plant; D013045:Species Specificity; D014158:Transcription, Genetic; D014908:Triticum / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D014867:Water
chemical_list: D018744:DNA, Plant; D010937:Plant Growth Regulators; D018749:RNA, Plant; D014867:Water; D008031:Lignin
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