PFKFB3 controls acinar IP3R-mediated Ca2+ overload to regulate acute pancreatitis severity.

Acute Pancreatitis (AP) is among the most common hospital gastrointestinal diagnosis; understanding the mechanisms underlying the severity of AP are critical for development of new treatment options for this disease. Here, we evaluate the biological function of phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in AP pathogenesis in two independent genetically engineered mouse models of AP. PFKFB3 is elevated in AP and severe AP (SAP) and knockout of Pfkfb3 abrogates the severity of alcoholic SAP (FAEE-SAP). Using a combination of genetic, pharmacological, and molecular studies we define the interaction of PFKFB3 with inositol 1,4,5-trisphosphate receptor (IP3R) as a key event mediating this phenomenon. Further analysis demonstrated that the interaction between PFKFB3 and IP3R promotes FAEE-SAP severity by altering intracellular calcium homeostasis in acinar cells. Together our results support a PFKFB3-driven mechanism controlling AP pathobiology and define this enzyme as a therapeutic target to ameliorate the severity of this dismal condition.

XAF1 Protects Host against Emerging RNA Viruses by Stabilizing IRF1-Dependent Antiviral Immunity.

XIAP-associated factor 1 (XAF1) is an interferon (IFN)-stimulated gene (ISG) that enhances IFN-induced apoptosis. However, it is unexplored whether XAF1 is essential for the host fighting against invaded viruses. Here, we find that XAF1 is significantly upregulated in the host cells infected with emerging RNA viruses, including influenza, Zika virus (ZIKV), and SARS-CoV-2. IFN regulatory factor 1 (IRF1), a key transcription factor in immune cells, determines the induction of XAF1 during antiviral immunity. Ectopic expression of XAF1 protects host cells against various RNA viruses independent of apoptosis. Knockout of XAF1 attenuates host antiviral innate immunity in vitro and in vivo, which leads to more severe lung injuries and higher mortality in the influenza infection mouse model. XAF1 stabilizes IRF1 protein by antagonizing the CHIP-mediated degradation of IRF1, thus inducing more antiviral IRF1 target genes, including DDX58, DDX60, MX1, and OAS2. Our study has described a protective role of XAF1 in the host antiviral innate immunity against RNA viruses. We have also elucidated the molecular mechanism that IRF1 and XAF1 form a positive feedback loop to induce rapid and robust antiviral immunity. IMPORTANCE Rapid and robust induction of antiviral genes is essential for the host to clear the invaded viruses. In addition to the IRF3/7-IFN-I-STAT1 signaling axis, the XAF1-IRF1 positive feedback loop synergistically or independently drives the transcription of antiviral genes. Moreover, XAF1 is a sensitive and reliable gene that positively correlates with the viral infection, suggesting that XAF1 is a potential diagnostic marker for viral infectious diseases. In addition to the antitumor role, our study has shown that XAF1 is essential for antiviral immunity. XAF1 is not only a proapoptotic ISG, but it also stabilizes the master transcription factor IRF1 to induce antiviral genes. IRF1 directly binds to the IRF-Es of its target gene promoters and drives their transcriptions, which suggests a unique role of the XAF1-IRF1 loop in antiviral innate immunity, particularly in the host defect of IFN-I signaling such as invertebrates.

Triptolide inhibits neutrophil extracellular trap formation.

BACKGROUND: Triptolide (PG490), as a triterpene dicyclic oxide has been reported to increase the generation of reactive oxygen species (ROS) and nitric oxide (NO) and induce apoptosis of RAW 264.7 cells in a dose-dependent manner. The activity of death NETs plays an important role in anti-bacterial processes in the human body. This study aimed to investigate the effect of triptolide (PG490) on neutrophil extracellular traps (NETs) formation. METHODS: After isolating peripheral blood neutrophils from healthy volunteers, cells were incubated with PG490 to observe and detect the level of NETs and detect the level of reactive oxygen species (ROS). The cells were cultured, stained and analyzed by fluorescence microscopy. RESULTS: Compared with the 12-myristate-13-acetate (PMA) group, the average fluorescence intensity of SYTOX Green in the PG490 + PMA group, as detected by a multifunctional microplate reader, was significantly decreased. Intracellular ROS were labeled by fluorescence, with fluorescence intensity then measured by multifunctional microplate reader and flow cytometry. The results showed that compared with the control group, the fluorescence intensity of the PMA group was significantly increased, while there was no significant difference between PMA group and PG490 + PMA group. CONCLUSIONS: The production of NETs is inhibited by PG490 in vitro, which is not associated with the level of cellular ROS. This suggests that PG490in Tripterygium wilfordii Hook F can suppress related diseases.

IFI16 Isoforms with Cytoplasmic and Nuclear Locations Play Differential Roles in Recognizing Invaded DNA Viruses.

IFN-γ-inducible protein 16 (IFI16) recognizes viral DNAs from both nucleus-replicating viruses and cytoplasm-replicating viruses. Isoform 2 of IFI16 (IFI16-iso2) with nuclear localization sequence (NLS) has been studied extensively as a well-known DNA sensor. However, the characteristics and functions of other IFI16 isoforms are almost unknown. Here, we find that IFI16-iso1, with exactly the same length as IFI16-iso2, lacks the NLS and locates in the cytoplasm. To distinguish the functions of IFI16-iso1 and IFI16-iso2, we have developed novel nuclear viral DNA mimics that can be recognized by the nuclear DNA sensors, including IFI16-iso2 and hnRNPA2B1. The hexanucleotide motif 5'-AGTGTT-3' DNA form of the nuclear localization sequence (DNLS) effectively drives cytoplasmic viral DNA nuclear translocation. These nuclear viral DNA mimics potently induce IFN-ß and antiviral IFN-stimulated genes in human A549 cells, HEK293T cells, and mouse macrophages. The subcellular location difference of IFI16 isoforms determines their differential functions in recognizing viral DNA and activating type I IFN-dependent antiviral immunity. IFI16-iso1 preferentially colocalizes with cytoplasmic HSV60mer and cytoplasm-replicating vaccinia virus (VACV), whereas IFI16-iso2 mainly colocalizes with nuclear HSV60-DNLS and nucleus-replicating HSV-1. Compared with IFI16-iso2, IFI16-iso1 induces more transcription of IFN-ß and IFN-stimulated genes, as well as stronger antiviral immunity upon HSV60mer transfection or VACV infection. IFI16-iso2, with the ability of nuclear-cytoplasmic shuttling, clears both invaded HSV type 1 and VACV significantly. However, IFI16-iso2 induces more type I IFN-dependent antiviral immunity than IFI16-iso1 upon HSV60-DNLS transfection or HSV type 1 infection. Our study has developed potent agonists for nuclear DNA sensors and also has demonstrated that IFI16 isoforms with cytoplasmic and nuclear locations play differential roles in innate immunity against DNA viruses.

STING-mediated degradation of IFI16 negatively regulates apoptosis by inhibiting p53 phosphorylation at serine 392.

Interferon-γ-inducible factor 16 (IFI16) triggers stimulator of interferon (IFN) genes (STING)-dependent type I IFN production during host antiviral immunity and facilitates p53-dependent apoptosis during suppressing tumorigenesis. We have previously reported that STING-mediated IFI16 degradation negatively regulates type I IFN production. However, it is unknown whether STING also suppresses IFI16/p53-dependent apoptosis via degradation of IFI16. Here, our results from flow cytometry apoptosis detection and immunoblot assays show that IFI16 and nutlin-3, a p53 pathway activator, synergistically induce apoptosis in U2OS and A549 cells. Protein kinase R-triggered phosphorylation of p53 at serine 392 is critical for the IFI16-p53-dependent apoptosis. However, overexpression of STING suppresses p53 serine 392 phosphorylation, p53 transcriptional activity, expression of p53 target genes, and p53-dependent mitochondrial depolarization and apoptosis. In summary, our current study demonstrates that STING-mediated IFI16 degradation negatively regulates IFI16-mediated p53-dependent apoptosis in osteosarcoma and non-small cell lung cancer cells, which suggests a protumorigenic role for STING in certain cancer types because of its potent ability to degrade upstream IFI16.

Berberine alleviates cisplatin-induced acute kidney injury by regulating mitophagy via PINK 1/Parkin pathway.

BACKGROUND: To study the protective effect of berberine (BBR) on cisplatin-induced acute kidney injury (AKI) and its effect on mitophagy. METHODS: (I) Male C57BL/6 mice aged 6-8 weeks were randomly divided into control group (saline), cisplatin group (cisplatin), and cisplatin + BBR (5, 10 mg/kg) groups. In the cisplatin group and BBR groups, mice were injected intraperitoneally with 15 mg/kg of cisplatin. Mice in BBR groups were given BBR at 72, 48, 24, 0.5 h before and 24, 48 h after cisplatin injection. Mice were sacrificed 72 h after cisplatin injection, and blood were collected for detecting serum creatinine (SCr) and blood urea nitrogen (BUN) levels. Kidneys were collected for detecting protein expression levels of Kidney injury molecule 1 (KIM-1), LC3 II/LC3 I, p62, PINK 1, Parkin in the renal tissue by Western blotting. The pathological changes in renal tissues were observed using periodic acid-Schiff (PAS) staining. (II) Renal tubular epithelial cells (RTECs) were pretreated with different concentrations (1, 2, and 4 µM) of BBR, and then incubated with cisplatin. Changes in autophagy proteins LC3 II/LC3 I, p62, PINK 1, and Parkin were detected by Western blotting, and changes in cellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were detected by flow cytometry. RESULTS: (I) Mice treated with BBR at dosage of 5 and 10 mg/kg for 6 days showed significant reduction in SCr and BUN compared to that in mice treated with cisplatin. PAS staining and immunohistochemistry showed that BBR ameliorated cisplatin-induced nephrotoxicity and reduced cisplatin-induced increase in protein expression levels of KIM-1. Compared to cisplatin-treated mice, the mice treated with BBR showed increased LC3 II/LC3 I, PINK 1, and Parkin, and decreased p62 protein expression. (II) Compared to cisplatin-incubated RTECs, cells pretreated with BBR for 24 h exhibited increased protein expressions of LC3 II/LC3 I, PINK1, and Parkin and decreased protein expression of p62. BBR reversed cellular ROS and cell MMP level induced by cisplatin. CONCLUSIONS: BBR plays a protective role in cisplatin-induced AKI by up-regulating mitophagy in RTECs.

[Total glucosides of paeony inhibits proliferation and promotes activation- induced cell death of mouse T cells in vitro].

OBJECTIVE: To investigate the effects of total glucosides of paeony (TGP) on the proliferation and activation-induced cell death of mouse T cells and the mechanism underlying the immunosuppressive effects of TGP. METHODS: Purified total T cells isolated from the spleen of C57BL/6 mice were treated with TGP at 0, 50, 100, or 200 µg/mL and stimulated by anti-CD3/ CD28. Flow cytometry was performed to detect the cell death and the proliferation of CFSE-labeled T cells. The expression of Fas/FasL mRNA was detected using RT-PCR, and flow cytometry was used to analyze the expression of Fas/FasL proteins on activated T cells. Western blotting was used to detect the expression of Bcl-2 in the cells. RESULTS: TGP treatment for 48 h significantly reduced the total number and percentage of viable T cells and dose-dependently lowered the percentage of divided T cells. TGP treatment obviously up-regulated the cellular expression of Fas mRNA, enhanced Fas expression on the surface of the T cells, and decreased the expression level of Bcl-2 protein in the cells. CONCLUSIONS: TGP significantly inhibits proliferation and promotes activation-induced cell death of mouse T cell by increasing the expression of Fas and downregulating the expression of Bcl-2.

STING-Mediated IFI16 Degradation Negatively Controls Type I Interferon Production.

γ-interferon-inducible protein-16 (IFI16), a key DNA sensor, triggers downstream STING-dependent type I interferon (IFN-I) production and antiviral immunity. However, it is still unclear how to negatively regulate IFI16 to avoid excessive IFN-I production and autoimmunity. Here, we find that STING directly interacts with IFI16 and facilitates IFI16 degradation via the ubiquitin-proteasome pathway by recruiting the E3 ligase TRIM21. The 1-pyrin region of IFI16 is responsible for the IFI16-STING interaction, and the first three lysines in the N-terminal region of IFI16 are the key sites that lead to STING-mediated IFI16 ubiquitination and degradation. Compared to wild-type IFI16, a higher level of viral DNA triggered IFN-ß and antiviral IFN-stimulated gene expression, and thus less HSV-1 infection, was observed in the cells transfected with IFI16-K3/4/6R, an IFI16 mutant that is resistant to degradation. STING-mediated negative feedback regulation of IFI16 restricts IFN-I overproduction during antiviral immunity to avoid autoimmune diseases.

Sonodynamic Therapy Combined to 2-Deoxyglucose Potentiate Cell Metastasis Inhibition of Breast Cancer.

Metastasis is a major dilemma of cancer therapy. It frequently occurs in breast cancer, which is the leading form of malignant tumor among females worldwide. Although there are therapies that provide a possible method for this challenge, such as chemotherapy, the tumoral metabolic pathway is unconventional and favors metastasis and proliferation. This magnifies the difficulty of treating breast cancer. In this study, we identified 2-deoxyglucose (2 DG) as an important glycolysis suppressor that can potentiate sonodynamic therapy (SDT) to inhibit migration and invasion. In addition, disruptions of the cell membrane microstructure were captured by a scanning electron microscope in cells treated with the co-therapy. Similarly, we detected blockages of the cell cycle process, using flow cytometry. Of note, we observed that hexokinase II (HK2), the rate-limiting enzyme of glycolysis, was notably uncoupled from the mitochondria in SDT + 2 DG co-therapy group. Furthermore, there was altered expression of HK2 and Glut1, which control glycolysis. Simultaneously, the in vivo results revealed that pulmonary metastasis was also seriously suppressed by SDT + 2 DG co-therapy. These results demonstrate this co-therapy is a promising strategy for breast cancer inhibition through metastasis and proliferation.

2-deoxy-D-glucose augments photodynamic therapy induced mitochondrial caspase-independent apoptosis and energy-mediated autophagy.

OBJECTIVES: Compared to normal cells, malignant cells have a high degree of aerobic glycolysis, also known as the Warburg effect. Therefore, supplementing photodynamic therapy (PDT), an established cancer therapy, with metabolic inhibitors can augment the mitochondrial damage by depleting ATP. To assess the combined impact of the glycolysis inhibitor 2-deoxy-D-glucose (2-DG) and PDT on apoptosis and autophagy in human breast cancer cells, and examine the molecular basis. METHODS: Calcium-AM/PI double staining was used to evaluate cell viability. Reactive oxygen species (ROS), mitochondria membrane potential (MMP), nuclear morphology, and autophagosomes were measured using specific fluorescent markers. In addition, translocation of the apoptosis inducing factor (AIF) from the mitochondria to nucleus was imaged by confocal laser scanning microscopy, and DNA fragmentation was measured using PI staining and comet assay. PGC-1α expression, oxidative phosphorylation, ATP levels, and autophagy related proteins were detected by qRT-PCR, seahorse bioscience XFP extracellular flux analyzer, and Western blotting, respectively. RESULTS: Compared to with either monotherapy, 2-DG+PDT resulted in significantly higher cytotoxicity in the three breast cancer cell lines (MDA-MB-231, MCF-7, and 4T1), which was consistent with tumor growth regression trends seen in the 4T1 xenograft model. A synergistic augmentation of mitochondrial dysfunction (in terms of ROS generation, MMP loss, and PGC-1α down-regulation) and ATP depletion was seen in cells receiving 2-DG and PDT. In addition, nuclear translocation of AIF and the subsequent DNA damage indicated that the cytotoxic effects were mediated by a caspase-independent mechanism, which was relieved by the ROS scavenger N-acetylcysteine. Autophagy via the AMP-activated protein kinase (AMPK) was also observed following 2-DG+PDT, and reversed upon pre-treatment with the autophagy inhibitor 3-methyladenine. CONCLUSIONS: The anti-cancer effects of 2-DG+PDT are mediated by both mitochondria triggered apoptosis and AMPK-mediated autophagy. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc.

Synthesis, Characterization, and Biological Evaluation of a Porphyrin-Based Photosensitizer and Its Isomer for Effective Photodynamic Therapy against Breast Cancer.

A photosensitizer with high phototoxicity, low dark toxicity, and good water solubility is crucial for effective photodynamic therapy (PDT). In this study, a novel class of porphyrin-based water-soluble derivative and its isomers, named photohexer-1 (P-1) and photohexer-2 (P-2), were synthesized and investigated for anticancer activity. Both of the isomers, P-1 and P-2, could be utilized as potential sensitizers for PDT not only owing to their definite constituents but predominantly due to their good absorption in the phototherapeutic window and high generation of intracellular ROS. Therein, P-2 exhibited stronger phototoxicity against breast cancer cells with weaker dark toxicity than P-1; however, both P-1 and P-2 were highly phototoxic as compared to their homologous compound, hematoporphyrin monomethyl ether (HMME). These findings were consistent with the antitumor efficacy in vivo. Moreover, P-1 and P-2 could both effectively localize in multiple subcellular organelles, triggering increased cellular apoptosis or necrosis under laser irradiation as compared to HMME. In conclusion, the findings of the study suggest that the two highly water-soluble porphyrin derivatives may serve as promising putative photosensitizers for improving the therapeutic efficiency of PDT.

Blocking the Glycolytic Pathway Sensitizes Breast Cancer to Sonodynamic Therapy.

Inhibition of the increased aerobic glycolysis in cancer cells is a promising methodology for various malignant tumor therapies but is limited by systemic toxicity, at least in part. Recent studies suggest that dual restriction of glycolysis and mitochondrial function may overcome this issue. Sonodynamic therapy (SDT), a prospective therapeutic modality for cancers, has been reported to induce mitochondria-dependent cell damage. Here, we investigated the combined effect of SDT and 2-deoxyglucose (2DG), an anti-glycolytic agent, on breast cancer both in vitro and in vivo. In vitro, we found that, compared with a single treatment, SDT + 2DG co-treatment significantly decreased cell viability and increased cell apoptosis. Moreover, the generation of reactive oxygen species was enhanced and mitochondrial membrane potential (MMP) was reduced after SDT + 2DG co-treatment. Furthermore, the oxidative phosphorylation was also restrained after SDT + 2DG co-treatment, further to cause the blockage of ATP provision. In vivo, SDT + 2DG markedly reduced tumor volume and weight, consistent with the in vitro findings. Furthermore, toxicology tests concurrently indicated that the dosages of sinoporphyrin sodium and 2DG were comparatively tolerable. Generally, these results indicated that SDT + 2DG combination therapy may be an available, promising therapy for highly metastatic breast cancer.

Improving protein content and quality by over-expressing artificially synthetic fusion proteins with high lysine and threonine constituent in rice plants.

Rice grains are rich in starch but low in protein with very low level of both lysine and threonine. Thus, it is important to further improve protein quality and quantity, especially to increase lysine and threonine content in rice grains. We artificially synthesized two new genes by fusing endogenous rice genes with lysine (K)/threonine (T) motif (TKTKK) coding sequences. They were designated as TKTKK1 and TKTKK2 and their encoded proteins consist of 73.1% and 83.5% of lysine/threonine, respectively. These two genes were under the control of 35S promoter and were independently introduced into the rice genome to generate transgenic plants. Our data showed that overexpression of TKTKK1 generated stable proteins with expected molecular weight and the transgenic rice seeds significantly increased lysine, threonine, total amino acids and crude protein content by 33.87%, 21.21%, 19.43% and 20.45%, respectively when compared with wild type control; significant improvement was also observed in transgenic rice seeds overexpressing TKTKK2. However, limited improvement in protein quality and quantity was observed in transgenic seeds carrying tandom array of these two new genes. Our data provide the basis and alternative strategy on further improving protein quality and quantity in other crops or vegetable plants by synthetic biology.

Engineering low phorbol ester Jatropha curcas seed by intercepting casbene biosynthesis.

KEY MESSAGE: Casbene is a precursor to phorbol esters and down-regulating casbene synthase effectively reduces phorbol ester biosynthesis. Seed-specific reduction of phorbol ester (PE) helps develop Jatropha seed cake for animal nutrition. Phorbol esters (PEs) are diterpenoids present in some Euphorbiaceae family members like Jatropha curcas L. (Jatropha), a tropical shrub yielding high-quality oil suitable as feedstock for biodiesel and bio jet fuel. Jatropha seed contains up to 40 % of oil and can produce oil together with cake containing high-quality proteins. However, skin-irritating and cancer-promoting PEs make Jatropha cake meal unsuitable for animal nutrition and also raise some safety and environmental concerns on its planting and processing. Two casbene synthase gene (JcCASA163 and JcCASD168) homologues were cloned from Jatropha genome and both genes were highly expressed during seed development. In vitro functional analysis proved casbene synthase activity of JcCASA163 in converting geranylgeranyl diphosphate into casbene which has been speculated to be the precursor to PEs. A seed-specific promoter driving inverted repeats for RNAi interference targeting at either JcCASA163 or both genes could effectively down-regulate casbene synthase gene expression with concurrent marked reduction of PE level (by as much as 85 %) in seeds with no pleiotropic effects observed. Such engineered low PE in seed was heritable and co-segregated with the transgene. Our work implicated casbene synthase in Jatropha PE biosynthesis and provided evidence for casbene being the precursor for PEs. The success in reducing seed PE content through down-regulation of casbene synthase demonstrates the feasibility of intercepting PE biosynthesis in Jatropha seed to help address safety concerns on Jatropha plantation and seed processing and facilitate use of its seed protein for animal nutrition.

Characterization of the complete mitochondrial genome of the Rhinolophus sinicus sinicus (Chiroptera: Rhinolophidae) from Central China.

We present a complete mitochondrial genome sequence of Rhinolophus sinicus sinicus from Central China and provide its annotation, as well as showed the phylogenetic relationship and mitogenomic variation with other published mitochondrial genomes of congeneric bat species. Our results revealed a relatively high mitogenomic variation between two R. s. sinucus from Central and East China, which is similar to interspecific divergence level.

A mutation in Thermosensitive Male Sterile 1, encoding a heat shock protein with DnaJ and PDI domains, leads to thermosensitive gametophytic male sterility in Arabidopsis.

In most flowering plant species, pollination and fertilization occur during the hot summer, so plants must have evolved a mechanism that ensures normal growth of their pollen tubes at high temperatures. Despite its importance to plant reproduction, little is known about the molecular basis of thermotolerance in pollen tubes. Here we report the identification and characterization of a novel Arabidopsis gene, Thermosensitive Male Sterile 1 (TMS1), which plays an important role in thermotolerance of pollen tubes. TMS1 encodes a Hsp40-homologous protein with a DnaJ domain and an a_ERdj5_C domain found in protein disulfide isomerases (PDI). Purified TMS1 expressed in Escherichia coli (BL21 DE3) had the reductive activity of PDI. TMS1 was expressed in pollen grains, pollen tubes and other vegetative tissues, including leaves, stems and roots. Heat shock treatment at 37 degrees C increased its expression levels in growing pollen tubes as well as in vegetative tissues. A knockout mutation in TMS1 grown at 30 degrees C had greatly retarded pollen tube growth in the transmitting tract, resulting in a significant reduction in male fertility. Our study suggests that TMS1 is required for thermotolerance of pollen tubes in Arabidopsis, possibly by functioning as a co-molecular chaperone.

Overexpression of TAPETUM DETERMINANT1 alters the cell fates in the Arabidopsis carpel and tapetum via genetic interaction with excess microsporocytes1/extra sporogenous cells.

Previously, we reported that the TAPETUM DETERMINANT1 (TPD1) gene is required for specialization of tapetal cells in the Arabidopsis (Arabidopsis thaliana) anther. The tpd1 mutant is phenotypically identical to the excess microsporocytes1 (ems1)/extra sporogenous cells (exs) mutant. The TPD1 and EMS1/EXS genes may function in the same developmental pathway in the Arabidopsis anther. Here, we further report that overexpression of TPD1 alters the cell fates in the Arabidopsis carpel and tapetum. When TPD1 was expressed ectopically in the wild-type Arabidopsis carpel, the number of cells in the carpel increased significantly, showing that the ectopic expression of TPD1 protein could activate the cell division in the carpel. Furthermore, the genetic analysis showed that the activation of cell division in the transgenic carpel by TPD1 was dependent on EMS1/EXS, as it did not happen in the ems1/exs mutant. This result further suggests that TPD1 regulates cell fates in coordination with EMS1/EXS. Moreover, overexpression of TPD1 in tapetal cells also delayed the degeneration of tapetum. The TPD1 may function not only in the specialization of tapetal cells but also in the maintenance of tapetal cell fate.

Genetic and molecular identification of genes required for female gametophyte development and function in Arabidopsis.

The plant life cycle involves an alternation of generations between sporophyte and gametophyte. Currently, the genes and pathways involved in gametophytic development and function in flowering plants remain largely unknown. A large-scale mutant screen of Ds transposon insertion lines was employed to identify 130 mutants of Arabidopsis thaliana with defects in female gametophyte development and function. A wide variety of mutant phenotypes were observed, ranging from defects in different stages of early embryo sac development to mutants with apparently normal embryo sacs, but exhibiting defects in processes such as pollen tube guidance, fertilization or early embryo development. Unexpectedly, nearly half of the mutants isolated in this study were found to be primarily defective in post-fertilization processes dependent on the maternal allele, suggesting that genes expressed from the female gametophyte or the maternal genome play a major role in the early development of plant embryos. Sequence identification of the genes disrupted in the mutants revealed genes involved in protein degradation, cell death, signal transduction and transcriptional regulation required for embryo sac development, fertilization and early embryogenesis. These results provide a first comprehensive overview of the genes and gene products involved in female gametophyte development and function within a flowering plant.