- [Show abstract] [Hide abstract] ABSTRACT: Heat shock proteins (Hsps) are a family of highly conserved proteins present in all organisms. They mediate a range of cytoprotective functions as molecular chaperones and are recently reported to regulate the immune response. Using suppression subtractive hybridization, we isolated and characterized a cucumber cDNA, designated CsHsp45.9, which encodes a putative heat shock protein of 45.9 kDa protein, containing three conserved DnaJ domains belonging to the Type I Hsp40 family. Real-time quantitative RT-PCR analysis revealed that CsHsp45.9 was significantly induced in cucumber leaves inoculated with downy mildew (Pseudoperonospora cubensis) in this incompatible interaction. Gene expression was also strongly up-regulated by various abiotic stresses. CsHsp45.9 was mainly expressed in flowers with a flower-specific, stamen- and pistil-predominant expression pattern. This suggests that CsHsp45.9 harbors broad-spectrum responses to both biotic and abiotic stresses and may play a role in downy mildew resistance in cucumber.
- [Show abstract] [Hide abstract] ABSTRACT: A simple procedure has been outlined for plant regeneration of Amorphophallus albus Liu & Wei, a native medicinal plant in China, from petiole-derived callus. Calli were induced at a high frequency of 76.4±3.2% from petiole explants excised from two-month-old plants on Murashige and Skoog (MS) medium supplemented with 5.37 μM α-naphthaleneacetic acid (NAA) and 4.44 μM 6-benzyladenine (BA). Of the different types of callus induced, type III callus was selected for morphogenesis induction. Culture of the callus on MS medium containing proper NAA and BA or KT combinations resulted in formation of corm-like structure (CLS) that produced shoots and roots during further culture. The optimal morphogenetic response was observed on the media with a cytokinin/auxin ratio of about 4:1, which resulted in more than 70% CLS formation and 6∼8 CLSs per callus. Complete plantlets with well-developed root systems were obtained from these CLSs by subculturing them on the original media from which they had been derived without a separate rooting culture. Transfer of the plantlets with roots to soil resulted in a more than 90% survival rate. Analysis of 20 regenerated plants by two molecular markers, randomly amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR), revealed somaclonal variation in the regenerated plants. The percentage of polymorphic bands in RAPD and ISSR analysis were respectively 20.8% and 39.0% for the 20 plants. Cluster analysis indicated that the genetic similarity values calculated on the basis of RAPD and ISSR data among the 21 plants (20 regenerated and one donor plant) were, respectively, 0.973 and 0.917, which allowed classification of the plants into distinct groups. A high-frequency somaclonal variation induced in A. albus tissue culture may help in the selection of useful variants that may be induced to improve this important corp.
- [Show abstract] [Hide abstract] ABSTRACT: Two different morphogenetic pathways, adventitious bud and corm-like structure (CLS), were observed on organogenic calli derived from the petioles of Amorphophallus albus in vitro. The organogenic calli was established via culture of petiole segments on Murashige and Skoog (MS) medium supplemented with 1.0mgl−1 α-naphthaleneacetic acid (NAA) and 1.0mg l−1 6-benzyladenine (BA) and subculture of the petiole-derived calli on MS medium with 0.5mgl−1 NAA and 0.5mgl−1 BA. These organogenic calli were used to induce morphogenesis via culture on MS medium with various concentrations of NAA and BA. BA alone favoured adventitious bud differentiation (57.0±8.3% at maximum) from the organogenic calli but inhibited CLS formation. In the presence of NAA and BA, both adventitious bud and CLS were observed in a same culture system. The maximum CLS formation (71.2±9.3%) were found on MS medium with 0.5mgl−1 NAA and 2.0mgl−1 BA, associated with 26.7±8.6% adventitious bud differentiation. A small part of the adventitious buds developed into normal shoots which needed rooting culture phase to form complete plants. About 80% survival rate was obtained with these plants after transplantation to soil. More than 90% of the CLSs produced complete plants with shoots and root systems, regardless of the rooting media tested. Transplantation of the CLS-derived plants to soil gave 100% survival rate. Histological observations revealed both the two morphogenetic events originated from the meristematic cells located in superficial layers of callus tissue.