Delayed germination of Arabidopsis seeds under chilling stress by overexpressing an abiotic stress inducible GhTPS11.

Trehalose-6-phosphate synthase (TPS) plays an important role in metabolic regulation and stress responses in a variety of organisms. However information about cotton TPS is poor. Here a cotton TPS gene GhTPS11 was isolated and characterized. Expression analysis revealed that GhTPS11 was induced in 20-day old cotton seedlings by heat drought and high salt stresses as well as GA and ABA. Moreover GhTPS11 was induced by chilling stress and mannitol while was depressed by sucrose. Tissue expression analysis indicated that GhTPS11 expressed higher in leaves than in stems and roots of 20-day old cotton seedlings. The GhTPS11 overexpressing Arabidopsis seeds germinated slower than the wild-type (WT) under chilling stress. Trehalose-6-phosphate (T6P) and trehalose contents were evidently higher in GhTPS11 overexpressing lines 3, 5, and 22 than in WT under normal germination condition as well as chilling stress. Further analysis demonstrated that the expression of ICE1 CBF3 and RCI2A was induced lower whereas that of CBF1 and CBF2 was induced higher under chilling stress in the GhTPS11 overexpressing seeds than WT respectively. These results suggested that GhTPS11 encoded a stress-responsive TPS protein and functioned in chilling stress during seed germination. Perhaps the chilling stress sensitivity of transgenic Arabidopsis seeds was caused by the expression changes of at least some chilling-related genes such as ICE1 CBFs and RCI2A other than HOS1. So this article provided the useful information for GhTPS11 usage for crop molecular breeding.

A DExD/H box RNA helicase is important for K+ deprivation responses and tolerance in Arabidopsis thaliana.

The molecular mechanism for sensing and transducing the stress signals initiated by K(+) deprivation in plants remains unknown. Here, we found that the expression of AtHELPS, an Arabidopsis DExD/H box RNA helicase gene, was induced by low-K(+), zeatin and cold treatments, and downregulated by high-K(+) stress. To further investigate the expression pattern of AtHELPS, pAtHELPS::GUS transgenic plants were generated. Histochemical staining indicated that AtHELPS is mainly expressed in the young seedlings and vascular tissues of leaves and roots. Using both helps mutants and overexpression lines, we observed that, in the low-K(+) condition, AtHELPS affected Arabidopsis seed germination and plant weight. Interestingly, the mRNA levels of AKT1, CBL1/9 and CIPK23 in the helps mutants were much higher than in the overexpression lines under low-K(+) stress. Moreover, under low-K(+) stress, the helps mutants displayed increased K(+) influx, whereas the overexpression line of AtHELPS had a lower flux rate in the roots by the noninvasive micro-test technique. Taken together, these results provide information for the functional analysis of plant DEVH box RNA helicases, and suggest that AtHELPS, as an important negative regulator, plays a role in K(+) deprivation stress.

NtKTI1, a Kunitz trypsin inhibitor with antifungal activity from Nicotiana tabacum, plays an important role in tobacco's defense response.

A cDNA library from tobacco inoculated with Rhizoctonia solani was constructed, and several cDNA fragments were identified by differential hybridization screening. One cDNA clone that was dramatically repressed, NtKTI1, was confirmed as a member of the Kunitz plant proteinase inhibitor family. RT-PCR analysis revealed that NtKTI1 was constitutively expressed throughout the whole plant and preferentially expressed in the roots and stems. Furthermore, RT-PCR analysis showed that NtKTI1 expression was repressed after R. solani inoculation, mechanical wounding and salicylic acid treatment, but was unaffected by methyl jasmonate, abscisic acid and NaCl treatment. In vitro assays showed that NtKTI1 exerted prominent antifungal activity towards R. solani and moderate antifungal activity against Rhizopus nigricans and Phytophthora parasitica var. nicotianae. Bioassays of transgenic tobacco demonstrated that overexpression of NtKTI1 enhanced significantly the resistance of tobacco against R. solani, and the antisense lines exhibited higher susceptibility than control lines towards the phytopathogen. Taken together, these studies suggest that NtKTI1 may be a functional Kunitz trypsin inhibitor with antifungal activity against several important phytopathogens in the tobacco defense response.