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.

Based on sequencing of part clones in a root subtractive cDNA library, an expressed sequence tag (EST) sharing high similarity to a rice C2H2 zinc finger transcription factor (ZFP15) was obtained in wheat. Through bioinformatics approach, the wheat C2H2-type ZFP gene referred to TaZFP15 has been identified and characterized. As a full-length cDNA of 670 bp, TaZFP15 has an open reading frame of 408 bp and encodes a 135-aa polypeptide. TaZFP15 contains two C2H2 zinc finger domains and each one has a conserved motif QALGGH. The typical L-box, generally identified in the C2H2 type transcription factors, has also been found in TaZFP15. Phylogenetic analysis suggested that TaZFP15 shares high similarities with rice ZFP15 (GenBank accession no. AY286473), maize ZFP (GenBank accession no. NM_001159094) and a subset of other zinc-finger transcription factor genes in plant species. The expression of TaZFP15 was up-regulated by starved-Pi stress, showing a pattern to be gradually elevated along with the progression of the Pi-stress in a 23-h treatment regime. Similarly, the transcripts of TaZFP15 in roots were also induced by nitrogen deficiency, and abiotic stresses of drought and salinity. No responses of TaZFP15 were detected in roots to nutrition deficiencies of P, Zn, and Ca, and the external treatment of abscisic acid (ABA). TaZFP15 could be specifically amplified in genome A, B, and D, and without variability in the sequences, suggesting that TaZFP15 has multi-copies in the homologous hexaploid species. Transgenic analysis in tobacco revealed that up-regulation of TaZFP15 could significantly improve plant dry mass accumulation via increasing the plant phosphorus acquisition capacity under Pi-deficiency condition. The results suggested that TaZFP15 is involved in mediation of signal transductions of diverse external stresses.

Premature senescence in crop production, especially occurred at the late growth stage, generally results in a reduction inyield and quality. Therefore, it is beneficial for yield and quality to properly delay senescence of plant tissues during thelate developmental stage. In this study, it was observed that the chlorophyll content and photosynthetic rate weregradually decreased along leaf growth progression, and the rates of reduction were promoted by drought. Based on gaschromatography-mass spectrometry (GC-MS) analysis, total eight, five, seven, and five kinds of organic compounds thatputatively 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 α-pinene, β-pinene, and pentadecane werepresent in different tissues. Among the total ten organic substances identified to be related with the leaf senescence, halfwere specifically detected in the drought treatment. These results suggest some biochemical pathways associated withthe leaf senescence are distinctly regulated by drought. The identified organic compounds in the tested tissues showedthree types on the performance pattern based on the contents along with the senescent progression, including graduallyincreasing, decreasing, and a curve with one single peak. Thus, during the senescence process in tissues, a subset ofmetabolic substances occur modifications on the quantities, reflecting a complicate biochemical reactions are initiated viathe senescence signals. Further analysis of the important organic substances will be helpful for elucidation of the tissuesenescence mechanism at the biochemical level and provide a new insight of the senescence signaling transductions incotton.