DnaJ proteins constitute a DnaJ/Hsp40 family and are important regulators involved in diverse cellular functions. To date, the molecular mechanisms of DnaJ proteins involved in response to drought stress in plants are largely unknown. In this study, a putative DnaJ ortholog from Nicotiana tabacum (NtDnaJ1), which encodes a putative type-I J-protein, was isolated. The transcript levels of NtDnaJ1 were higher in aerial tissues and were markedly up-regulated by drought stress. Over-expression of NtDnaJ1 in Arabidopsis plants enhanced their tolerance to osmotic or drought stress. Quantitative determination of H2O2 accumulation has shown that H2O2 content increased in wild-type and transgenic seedlings under osmotic stress, but was significantly lower in both transgenic lines compared with the wild-type. Expression analysis of stress-responsive genes in NtDnaJ1-transgenic Arabidopsis revealed that there was significantly increased expression of genes involved in the ABA-dependent signaling pathway (AtRD20, AtRD22 and AtAREB2) and antioxidant genes (AtSOD1, AtSOD2, and AtCAT1). Collectively, these data demonstrate that NtDnaJ1 could be involved in drought stress response and its over-expression enhances drought tolerance possibly through regulating expression of stress-responsive genes. This study may facilitate our understandings of the biological roles of DnaJ protein-mediated abiotic stress in higher plants and accelerate genetic improvement of crop plants tolerant to environmental stresses.

Grafting has been used to induce abiotic stress tolerance in horticultural crops recently. However, few studies have come out with the effects of grafting and its possible molecular mechanism under drought conditions in tobacco. In this study, using the drought-tolerant cultivar Nongda202 as a rootstock and the drought-sensitive cultivar K326 as a scion, we exposed non-grafted (K326/K326), self-grafted (K326/K326) and rootstock-grafted (K326/Nongda202) tobacco plants to drought stress over a 12-day period, and investigated their differential physiological and molecular responses to drought stress. Our results showed that drought-induced inhibition of growth was significantly alleviated in rootstock-grafted plants, as was evidenced by the physiological indexes, such as much higher SOD and CAT activities, higher levels of proline accumulation and lower levels of lipid peroxidation. Further expression analysis by real-time PCR indicated that rootstock-grafting affected transcripts of stress-responsive genes NtAREB, NtCDPK2, NtLEA5 and NtERD10C in a prompt and lasting manner. Together, these results demonstrated that grafting with rootstock genotypes tolerant to drought could improve drought stress tolerance in tobacco by regulating antioxidant enzyme activities and stress-responsive gene expression. This study will facilitate to broaden our understanding of the regulatory machinery of grafting, and will accelerate potential application of the grafting technique in improving biotic and abiotic stress tolerance in crop plants. (C) 2014 Elsevier B.V. All rights reserved.

To clarify expression property of aquaporins(AQPs) under drought stress in tobacco,we cloned the coding sequence of the NtTIP1 by RT- PCR.Sequence analysis has shown that the open reading frame of NtTIP1 is 756 bp and encodes a protein with 251 aa.The structure prediction has also found that NtTIP1 contains six conserved transmembrane domains.Phylogenetic tree of TIPs based on different species has demonstrated that NtTIP1 has quite high similarities(80% ~ 97%) to TIP proteins from Solanaceae and Arabidopsis species.Quantitative real-time RT- PCR has revealed that the NtTIP1 transcript levels were higher in vegetative organs of tobacco,including stems,leaves and roots.Upon PEG 6000-induced drought stress,NtTIP1 showed contrasting expression patterns between the tolerant and sensitive varieties.The transcript levels of NtTIP1 were up-regulated significantly in the tolerant variety LJ 851,but down-regulated in the sensitive one JX 6007,indicating that the expression abundance of the NtTIP1 is tightly correlated to drought tolerance and NtTIP1 may play an important role in drought adaption in tobacco.

Inulin is a natural fructan,a plant storage carbohydrate in the body.Inulinase is the hydrolysis of inulin to β-2,1-D-glycosidic bonds fruit candy together a class of enzymes.With a lot of wild fungus strains for type,screens after DNS process to one produces the inulase high strain,and has conducted the fermentation condition research to it,in the inulin 3 %,protein peptone 3 %,pH 5.0,the culture temperature in 30～37 ℃ about,the table raises 48～50 h to obtain the enzyme activity to be as higher as 8～10 times than the preliminary strain.