The relation between oxidative damage and viability loss of excised embryonic axes of Antiaris toxicaria subjected to rapid drying with silica gel at 15 °C was studied. Changes of survival rate, accumulation of thiobarbituric acid-reactive substances (TBARs), activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and the permeability of cell membrane that was determined as relative electrolyte leakage (REL) were measured. The half-life moisture content (MC_L50) was 0.41 g H₂O/g DW (dry weight basis). During drying, the activities of SOD, CAT and APX increased until MC_L50, and declined thereafter. The generation speed of ^·O₂⁻, and content of H₂O₂ and TBARs remained steadily or even decreased at MC levels higher than MC_L50, demonstrating a low oxidative level in these axes. There was no significant correlation between viability loss and accumulation of reactive oxygen species or lipid peroxidation within the dehydration process until MC_L50. Whereas the increase in REL from the beginning of the drying process indicated that the cell membrane was damaged. In conclusion, under rapid drying with silica gel the viability loss of excised recalcitrant A. toxicaria axes seemed to be triggered by mechanical or physical damage, rather than metabolic damage.

Xin X, Jing XM, Liu Y, Song SQ (2010) Viability loss pattern under rapid dehydration of Antiaris toxicaria axes and its relation to oxidative damage. J. Integr. Plant Biol. 52(5), 434–441.

In search for components of mitogen-activated protein kinase (MAPK) cascades in maize (Zea mays) involved in response to abscisic acid (ABA) stimulus, a novel MAPK gene, ZmMPK3, from ABA-treated maize leaves cDNA was isolated and characterized. The full length of the ZmMPK3 gene is 1 520 bp and encodes a 376 amino acid protein with a predicted molecular mass of 43.5 kD and a pI of 5.83. ZmMPK3 contains all 11 MAPK conserved subdomains and the phosphorylation motif TEY. Amino acid sequence alignment revealed that ZmMPK3 shared high identity with group-A MAPK in plants. A time course (30–360 min) experiment using a variety of signal molecules and stresses revealed that the transcripts level of ZmMPK3 accumulated markedly and rapidly when maize seedlings were subjected to exogenous signaling molecules: ABA, H₂O₂, jasmonic acid and salicylic acid, various abiotic stimuli such as cold, drought, ultraviolet light, salinity, heavy metal and mechanical wounding. Its transcription was also found to be tissue-specific regulated. Here, we show that ABA and H₂O₂ induced a significant increase in the ZmMPK3 activity using immunoprecipitation and in-gel kinase assay. Furthermore, the results showed that the ZmMPK3 protein is localized mainly to the nucleus. These results suggest that the ZmMPK3 may play an important role in response to environmental stresses.

Wang J, Ding H, Zhang A, Ma F, Cao J, Jiang M (2010) A novel mitogen-activated protein kinase gene in maize (Zea mays), ZmMPK3, is involved in response to diverse environmental cues. J. Integr. Plant Biol. 52(5), 442–452.

Using a subtractive hybridization (SH)/cDNA-AFLP combinational approach, differentially expressed genes involved in the potato-Phytophthora infestans interaction were identified. These included genes potentially controlling pathogenesis or avr genes in P. infestans as well as those potentially involved in potato resistance or susceptibility to this pathogen. Forty-one differentially expressed transcript-derived fragments (TDFs), resulting from the interaction, were cloned and sequenced. Two TDFs, suggested as potential pathogenicity factors, have sequence similarity to N-succinyl diaminopimelate aminotransferase and a transcriptional regulator, TetR family gene, respectively. Two other TDFs, suggested as potential avr genes, have sequence similarity to an EST sequence from Avr4/Cf-4/Avr9/Cf-9 and a P. infestans avirulence-associated gene, respectively. Genes' expression and origin were confirmed using Southern blots, Northern blots and qRT-PCR. I.e., potential resistance gene DL81 was induced at 12 hpi in the moderately resistant cultivar, whereas it was down-regulated as early as 6 hpi in the susceptible cultivar. On the other hand, DL21 was induced at 6 hpi (3.38-fold) in response to the highly aggressive isolate (US8) and strongly up-regulated thereafter (25.13-fold at 120 hpi.), whereas it was only slightly up-regulated in response to the weakly aggressive isolate US11 (3.82-fold at 96 hpi), suggesting its potential involvement as a susceptibility gene.

Henriquez MA, Daayf F (2010) Identification and cloning of differentially expressed genes involved in the interaction between potato and Phytophthora infestans using a subtractive hybridization and cDNA-AFLP combinational approach. J. Integr. Plant Biol. 52(5), 453–467.

Salt-tolerant maize (STM) and salt-sensitive maize (SSM) were treated with 100 mM NaCl for 1, 3 and 6 d and the contents of Na⁺ and Cl⁻ (cps) of different organelles of leaf cells determined by X-ray microanalysis. The results showed that Na⁺ and Cl⁻ entered the cytoplasm, vacuole, chloroplast and apoplast simultaneously. When STM and SSM were treated in 100 mM NaCl at atmospheric pressure (−P) and with pressure equivalent to the osmotic pressure of the NaCl (+P), the dry weights of STM (+P) and SSM (+P) plants were greater than that of STM (−P) and SSM (−P) plants, showing that the inhibitory effect of salt on plant growth was at least partially due to the osmotic effect of the NaCl. When STM and SSM were treated with NaCl and iso-osmotic polyethlene glycol, the dry weights of plants given the iso-osmotic polyethlene glycol treatment were lower for both maize lines than that of the NaCl-treated plants. Our data show that under NaCl stress, both STM and SSM seedlings simultaneously suffered from osmotic and ion stresses.

Zhao KF, Song J, Fan H, Zhou S, Zhao M (2010) Growth response to ionic and osmotic stress of NaCl in salt-tolerant and salt-sensitive maize. J. Integr. Plant Biol. 52(5), 468–475.

Late blight is the most devastating potato disease and it also causes serious yield loss in tomato. Several disease resistance genes (R genes) to late blight have been cloned from potato in the past decade. However, the resistance mechanisms remain elusive. Tomato and potato belong to the botanical family Solanaceace and share remarkably conserved genome structure. Since tomato is a model system in genetic and plant pathology research, we used tomato to develop a powerful mutant screening system that will greatly facilitate the analysis of the signaling pathway of resistance to Phytophthora infestans. First we proved that the R3a transgenic tomatoes developed specific hypersensitive cell death response (HR) to P. infestans strains carrying the corresponding avirulence gene Avr3a, indicating that the signaling pathway from the R3a-Avr3a recognition to HR is conserved between potato and tomato. Second, we generated transgenic tomatoes carrying both R3a and Avr3a genes, with the latter under the control of a glucocorticiod-inducible promoter. Dexamethasone induced expression of Avr3a and resulted in localized HR. This versatile system can be used to construct a mutant library to screen surviving mutants whose resistance signal transduction was interrupted, providing the basis to identify key genes involved in the resistance to late blight in Solanaceae.

Jia Z, Cui Y, Li Y, Wang X, Du Y, Huang S (2010) Inducible positive mutant screening system to unveil the signaling pathway of potato late blight resistance. J. Integr. Plant Biol. 52(5), 476–484.

Based on the evidence that Al resistance is an inducible process and rice is an Al-resistant crop, identification of Al-responsive genes from rice may help to further clone Al-resistant genes in plants. Semi-quantitative and real-time polymerase chain reaction (PCR) is widely applied in gene transcriptional analyses, particularly for those genes with low transcript abundance. Normalization with proper endogenous control (EC) genes is critical for these two approaches in terms of reliability and precision. We first noticed that the expression of several commonly-used EC genes was depressed under Al stress, while sulfite reductase gene (SR) was stable throughout the Al treatment. The reliability of SR as an EC gene was further tested by analyzing the expression of a number of genes in response to Al challenge. Except for the consistent results obtained for the four previously-identified genes, nine additional genes were newly defined as Al-responsive in this study. Collectively, our results suggest that SR can be used as a novel EC gene for semi-quantitative and real-time PCR analysis of Al responsive genes, and that activated transport of silicon and stimulated metabolism of carotenoid and terpenoid could be involved in Al resistance in rice plants.

Zhang J, Yin Y, Wang Y, Peng X (2010) Identification of rice Al-responsive genes by semi-quantitative polymerase chain reaction using sulfite reductase as a novel endogenous control. J. Integr. Plant Biol. 52(5), 505–514.