title: A new tomato NAC (NAM/ATAF1/2/CUC2) transcription factor, SlNAC4, functions as a positive regulator of fruit ripening and carotenoid accumulation.
abstract: Fruit ripening in tomato (Solanum lycopersicum) is a complicated development process affected by both endogenous hormonal and genetic regulators and external signals. Although the role of NOR, a member of the NAC domain family, in mediating tomato fruit ripening has been established, its underlying molecular mechanisms remain unclear. To explore further the role of NAC transcription factors in fruit ripening, we characterized a new tomato NAC domain protein, named SlNAC4, which shows high accumulation in sepal and at the onset of fruit ripening. Various stress treatments including wounding, NaCl, dehydration and low temperature significantly increased the expression of SlNAC4. Reduced expression of SlNAC4 by RNA interference (RNAi) in tomato resulted in delayed fruit ripening, suppressed Chl breakdown and decreased ethylene synthesis mediated mainly through reduced expression of ethylene biosynthesis genes of system-2, and reduced carotenoids by alteration of the carotenoid pathway flux. Transgenic tomato fruits also displayed significant down-regulation of multiple ripening-associated genes, indicating that SlNAC4 functions as a positive regulator of fruit ripening by affecting ethylene synthesis and carotenoid accumulation. Moreover, we also noted that SlNAC4 could not be induced by ethylene and may function upstream of the ripening regulator RIN and positively regulate its expression. Yeast two-hybrid assay further revealed that SlNAC4 could interact with both RIN and NOR protein. These results suggested that ethylene-dependent and -independent processes are regulated by SlNAC4 in the fruit ripening regulatory network.
authors.affiliation: Key Laboratory of Biorheological Science and Technology (Chongqing University), Ministry of Education, Bioengineering College, Chongqing University, Chongqing 400044, PR China.
authors.forename: Mingku
authors.initials: M
authors.lastname: Zhu
authors.forename: Guoping
authors.initials: G
authors.lastname: Chen
authors.forename: Shuang
authors.initials: S
authors.lastname: Zhou
authors.forename: Yun
authors.initials: Y
authors.lastname: Tu
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Tingting
authors.initials: T
authors.lastname: Dong
authors.forename: Zongli
authors.initials: Z
authors.lastname: Hu
mesh_terms: D000595:Amino Acid Sequence; D053898:Biosynthetic Pathways / Q000235:genetics; D002338:Carotenoids / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D003001:Cloning, Molecular; D005030:Ethylenes / Q000378:metabolism; D005638:Fruit / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics; D016415:Sequence Alignment; D013312:Stress, Physiological / Q000235:genetics; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D005030:Ethylenes; D010940:Plant Proteins; D014157:Transcription Factors; D002734:Chlorophyll; D002338:Carotenoids; C036216:ethylene
keywords: Carotenoid; Ethylene; Fruit ripening; NAC transcription factor; RNAi; Tomato