Search

Zinc finger protein (ZFP) genes comprise a large and diverse gene family, and are involved in biotic and abiotic stress responses in plants. In this study, a total of 126 ZFP genes classified into various types in wheat were characterized and subjected to expression pattern analysis under inorganic phosphate (Pi) deprivation. The wheat ZFP genes and their corresponding GenBank numbers were obtained from the information of a 4×44K wheat gene expression microarray chip. They were confirmed by sequence similarity analysis and named based on their homologs in Brachypodium distachyon or Oriza sativa. Expression analysis based on the microarray chip revealed that these ZFP genes are categorized into 11 classes according to their gene expression patterns in a 24-h of Pi deprivation regime. Among them, ten genes were differentially up-regulated, ten genes differentially down-regulated, and two genes both differentially up- and down-regulated by Pi deprivation. The differentially up- or down-regulated genes exhibited significantly more or less transcripts at one, two, or all of the checking time points (1, 6, and 24 h) of Pi stress in comparison with those of normal growth, respectively. The both differentially up- and down-regulated genes exhibited contrasting expression patterns, of these, TaWRKY70;5 showed significantly up-regulated at 1 and 6 h and down-regulated at 24 h whereas TaAN1AN20-8;2 displayed significantly upregulated at 1 h and downregulated at 6 h under deprivation Pi condition. Real time PCR analysis confirmed the expression patterns of the differentially expressed genes obtained by the microarray chip. Our results indicate that numerous ZFP genes in wheat respond to Pi deprivation and have provided further insight into the molecular basis that plants respond to Pi deprivation mediated by the ZFP gene family.

As a specific type of acid phosphatses, phytases play diverse roles in plants by catalazing the degradation of phytic acid and its derivatives. In this study, a rice phytase gene referred to OsPHY1 has been functionally characterized. OsPHY1 contains a 1 620 bp of open reading frame, encoding a 539-aa polypeptide. A conserve domain metallophosphatase (MPP) (MPP_PAPs), generally harbored in phytase and purple acid phosphatases (PAP), was identified in OsPHY1 (residue 194-398). Phylogenetic analysis revealed that OsPHY1 shares high similarities with phytase genes and PAP-type genes that derived from diverse plant species. The OsPHY1 transcripts were detected to be abundant in germinating seeds, suggesting that this gene plays potential roles on degradation of seed phytic acid and its derivatives during the germination process. Biochemical analysis confirmed that OsPHY1 possesses strong catalytic activities on phytic acid-Na2, with optimal temperature of 57°C and suitable pH of 3.5. Based on transgene analysis, the putative role of OsPHY1 in plants on utilization of phytate was assessed. Under the condition that phytic acid-Na2 was used as sole P source, the OsPHY1-overexpressing tobacco plants behaved higher phytase activities, higher concentrations of Pi, more accumulative amount of total phosphorus, and much more improved growth traits than those of the control plants. Therefore, OsPHY1 is acted as an important component on degradation of the phytins during the seed germination process in rice. Also, OsPHY1 has a potential use on generation of elite crop germplasms with improved use efficiencies on phytate and its derivatives.

MicroRNAs (miRNAs) are non-coding small RNAs that regulate gene expression by translational repression or transcript degradation. Thus far, a large number of miRNAs have been identified from model plant species and the quantity of miRNAs has been functionally characterized in diverse plants. However, the molecular characterizations of the conserved miRNAs are still largely elusive in wheat. In this study, 32 wheat miRNAs (TaMIRs) currently released in the Sanger miRBase (the microRNA database) were selected to evaluate the expression patterns under conditions of non-stress (CK) and salt stress treatment. Based on the analysis of semiquantitative RT-PCR and quantitative real qRT-PCR, TaMIR159a, TaMIR160, TaMIR167, TaMIR174, TaMIR399, TaMIR408, TaMIR11124 and TaMIR1133 were found to have responses to salinity stress, with an upregulated pattern under salt stress treatment. Based on a BLAST search against the NCBI GenBank database, the potential targets of the salt-inducible wheat miRNAs were predicted. Except for TaMIR399 not being identified to have the putative target genes, other salt-inducible TaMIRs were found to possess 2 to 7 putative target genes. Together, our results suggest that a subset of miRNAs are involved in the mediation of salt stress signaling responses in wheat via their roles on the regulation of acted target genes at post-transcriptional and translation levels.

Premature senescence in crop production, especially occurred at the late growth stage, generally results in a reduction in yield and quality. Therefore, it is beneficial for yield and quality to properly delay senescence of plant tissues during the late developmental stage. In this study, it was observed that the chlorophyll content and photosynthetic rate were gradually decreased along leaf growth progression, and the rates of reduction were promoted by drought. Based on gas chromatography-mass spectrometry (GC-MS) analysis, total eight, five, seven, and five kinds of organic compounds that putatively associated with the tissue senescent progression were identified in leaves, fruit branches, petals, and sepals, respectively. It was found that the identified organic compound, such as a-pinene, β-pinene, and pentadecane were present in different tissues. Among the total ten organic substances identified to be related with the leaf senescence, half were specifically detected in the drought treatment. These results suggest some biochemical pathways associated with the leaf senescence are distinctly regulated by drought. The identified organic compounds in the tested tissues showed three types on the performance pattern based on the contents along with the senescent progression, including gradually increasing, decreasing, and a curve with one single peak. Thus, during the senescence process in tissues, a subset of metabolic substances occur modifications on the quantities, reflecting a complicate biochemical reactions are initiated via the senescence signals. Further analysis of the important organic substances will be helpful for elucidation of the tissue senescence mechanism at the biochemical level and provide a new insight of the senescence signaling transductions in cotton.

The objective of this study was to disclose the possible mechanism of tolerance to Pi-deficiency in wheat (Triticum aestivum L.) at the gene-expression level. Seedlings of wheat cultivar Shixin 828, which has high phosphorus use efficiency, were treated with 20 µmol L−1 Pi for short (1–6 h), medium (12–48 h), and long terms (72–144 h). The differentially expressed sequence tags (ESTs) were identified using complementary DNA-amplified fragment length polymorphism (cDNA-AFLP) technique. A total of 143 and 94 nonredundant differential ESTs with up- and down-regulated patterns were identified, of which 23, 54, and 66 ESTs enhanced expression after the short-, medium-, and long-term treatments, and 17, 39, and 38 ESTs declined expression after the 3 treatments, respectively. These ESTs were classified into several functional groups according to the BLAST analysis. The up-regulated ESTs, except for 44 with unknown function, confer functions of signal transduction, transcription regulation, metabolism, stress response, development, transport, and lipid metabolism. The down-regulated ESTs are involved in the above functions and protein synthesis and protein degradation. Under the Pi-deficient condition, some genes were specifically up-regulated, such as OsPTF1 and ZAT10 homologues and genes encoding mitogen activated protein kinase, calcium-dependent protein kinase and protein kinase, high-affinity phosphate transporter, peroxidase and glutathione S-transferase. These genes are conjectured to play important roles in promoting adaptation to Pi-deficient environment.

Argonaute (AGO) proteins play important roles in RNA silencing processes through formation of complexes with the mature microRNAs. In this study, a wheat AGO gene referred to TaAGO1, which shares high similarities to AtAGO1 in Arabidopsis and OsAGO1 in rice, was characterized. As a cDNA full length of 3747 bp, TaAGO1 encodes a 1099-aa polypeptide with a molecular weight of 122 kD and an isoelectric point (pI) of 9.52. Subcellular prediction analysis suggests that TaAGO1 is to target onto the cytoplasm after endoplasmic reticulum (ER) sorted. Similar to AtAGO1 and OsAGO1, TaAGO1 contains PIWI and DDH, two conserved domains in AGOs. Phylogenetic analysis indicated that TaAGO1 was possibly derived from different progenitors with its homologous across diverse plant species. The transcripts of TaAGO1 were significantly regulated by the stresses of phosphorus deprivation and dehydration, and exogenous treatment of abscisic acid (ABA), suggesting that this wheat AGO member also exerts roles on mediating above signaling transductions. Southern blotting analysis revealed that genome AA, SS, and DD, three diploids composing of the hexaploid wheat, all harbored two copies of TaAGO1. Down-regulation of TaAGO1 in wheat led to conspicuously phenotypic alterations of the young plantlets, with a variety of abnormal growth features. Taking the results in this study together, it was implicated that TaAGO1 exists as a subset of copies in wheat and plays critical roles on silencing of appropriate target genes via regulation of TaAGO1-MiRNAs complex formation. Key words : Wheat (Triticum aestivum L.), argonaute (AGO) gene 1, cloning, molecular characterization, antisense expression.