Overexpression of DnaK chaperone from a halotolerant cyanobacterium Aphanothece halophytica increases seed yield in rice and tobacco

Abstract

The DnaK/Hsp70 family is a molecular chaperone that binds non-native states of other proteins, and concerns to various physiological processes in the bacterial, plant and animal cells. Transgenic tobacco plants expressing a molecular chaperone DnaK from a halotolerant cyanobacterium Aphanothece halophytica show enhanced seed yields as well as enhanced tolerances for salt and heat stresses. High-temperature treatment during the reproductive stage decreased total dry weight of seeds in both transgenic and wild-type tobacco, but more severely in the wild-type. Transgenic tobacco plants exhibited higher activities of ascorbate peroxidase and catalase than wild-type plants. Similar results were obtained for salt stress during the reproductive stage. Transgenic rice plants expressing ApDnaK was also constructed. Transgenic rice plants exhibited the enhanced activities for Calvin-cycle enzymes, and showed faster growth and higher seed yield compared with the wild-type rice under normal growth conditions. Transgenic rice plants also showed enhanced tolerance for high temperature and salt stress compared with the wild-type rice. These results suggest a relation of increased folding activity with enhanced stress tolerance, increased seed yield, and total plant biomass. Key words:Aphanothece halophytica, chaperone, DnaK, high temperature stress, rice, salt tolerance, seed yield.Plant Biotechnology 25, 141-150 (2008) Original PaperAbbreviations: Ap, Aphanothece halophytica; CaMV, cauliflower mosaic virus; HSF, heat shock factor; Hsp, heat shock proteins; MS, Murashige and Skoog; PRK, phosphoribulokinase; FBPase, cytosolic fructose-1,6-bisphosphatase; SPS, sucrose phosphate synthetase. This article can be found at http://www.jspcmb.jp/ (HSF) of HSP was shown to confer the thermotolerance (Lee et al. 1995). The overexpressions of carrot small Hsp (Malik et al. 1999) and Arabidopsis Hsp101 (Queitsch et al. 2000;Hong and Vierling 2001) have shown to enhance the thermotolerance of their own cells. The overexpression of Arabidopsis small Hsp was shown to enhance the osmotolerance of Arabidopsis (Sun et al. 2001). We also showed that the overexpression of DnaK from a halotolerant cyanobacterium Aphanothece halophytica (ApDnaK) which was isolated from The Dead Sea, conferred the tolerances for salt (Sugino et al. 1999) and high temperature (Ono et al. 2001) in transgenic tobacco plants. However, all these studies did not show the effects of overexpression of HSP on crop yield as well as growth promotion. Crop yield is one of the most important factors for agriculture. ApDnaK was previously shown to exhibit extremely high protein folding activity even under high salinity conditions . Here, we report that the transgenic rice and tobacco plants expressing ApDnaK could increase the seed yield and plant biomass in the laboratory conditions. Materials and methods Construction of vector and transformationTobacco plant (Nicotiana tabacum cv. Petit Havana SR1) was transformed with the dnaK gene from A. halophytica as described ...

Cloning and expression of dnaK gene from Bacillus pumilus of hot water spring origin

“…coli . dnaK from various organisms have been shown to play a role in thermoregulation and enhance thermotolerance in A. thaliana ( Montero-Barrientos et al, 2010 ), tobacco ( Ono et al, 2001 ) and Rice ( Uchida et al, 2008 ). However the cellular mechanism of DnaK function under stress conditions are not fully understood ( Wang et al, 2004 ).…”

“…The role of dnak in thermoregulation is well established by gene expression studies at mRNA level ( Wetzstein et al, 1992 ) and deletion mutation studies ( Singh et al, 2007 ). Enhancement of thermotolerance in the heterologous system has been reported in various organisms like Escherichia coli ( Liang et al, 2009 ), tobacco ( Ono et al, 2001 ), Arabidopsis thaliana ( Montero-Barrientos et al, 2010 ) and Rice ( Uchida et al, 2008 ). dnaK gene from Trichoderma harzianum has been found to enhance tolerance to drought and freezing stress in poplar ( Takabe et al, 2008 ).…”

Role of Heat Shock Proteins in Improving Heat Stress Tolerance in Crop Plants

“…Hsp70's have been reported to be involved in ABA responses, redox signalling, chloroplast development, and protein translocation into chloroplasts and mitochondria and hence over expression of this class of chaperons leads to increased resistance against drought, high salt and heat stresses in plants (Lee et al 2012 ). A halotolerant cynobacterial Hsp70/DnaK gene, when over expressed in tobacco and rice exhibited increased levels of anti-oxidant enzymes and enzymes involved in Calvin cycle conferring temperature and drought stress tolerance particularly during reproductive stage (Uchida et al 2008 ). The over expression of Hsp70 from fungus Trichoderma harzianum in A. thaliana resulted in increased level of Na/H transporter (SOS1) and APX1 with decreased levels of Hsf and Hsp transcripts (Montero-Barrientos et al 2010 ).…”

Engineering crop plants against abiotic stress: Current achievements and prospects

“…A comprehensive review article written by Grover et al (2013) discusses the types of heat shock families and also enlists the crop plants that have been transformed with heat shock protein genes. In addition to model plants, crop plants like tomato (Neta-sharir et al, 2005) rice (Uchida et al, 2008;Qi et al, 2011) tobacco (Uchida et al, 2008;Sun et al, 2012) soybean (Xhu et al, 2006 and cotton (Maqbool et al, 2010) have been reported in the literature. Neta-Sharir et al (2005) overexpressed HSP21 in tomato under 35S CaMV promoter and observed protected photosystem II (PSII) from temperature dependent oxidative stress.…”