Advances of Apetala2/Ethylene Response Factors in Regulating Development and Stress Response in Maize.

Apetala2/ethylene response factor (AP2/ERF) is one of the largest families of transcription factors, regulating growth, development, and stress response in plants. Several studies have been conducted to clarify their roles in Arabidopsis and rice. However, less research has been carried out on maize. In this review, we systematically identified the AP2/ERFs in the maize genome and summarized the research progress related to AP2/ERF genes. The potential roles were predicted from rice homologs based on phylogenetic and collinear analysis. The putative regulatory interactions mediated by maize AP2/ERFs were discovered according to integrated data sources, implying that they involved complex networks in biological activities. This will facilitate the functional assignment of AP2/ERFs and their applications in breeding strategy.

The lotus NnFTIP1 and NnFT1 regulate flowering time in Arabidopsis.

In higher plants, floral signals are mainly collected and transduced to FLOWERING LOCUS T (FT) in Arabidopsis and its orthologues. The movement of FT from leaves to the shoot apical meristem (SAM) is partially mediated by FT-INTERACTING PROTEIN1 (FTIP1). Although the functions of OsFTIP1 in rice and DOFTIP1 in orchid in FT transport have also been investigated, the FTIP1 homologue in lotus (Nelumbo nucifera Gaertn.), a type of horticultural plant with high economic and cultural value, has not been isolated, and the mechanism of NnFT1 transport has not been explored. Here, we revealed that NnFTIP1 mediates the transport of NnFT1 in ectopic transgenic lines in Arabidopsis. Overexpression of NnFTIP1 in the ftip1-1 background rescued the late flowering phenotype of ftip1-1, indicating that NnFTIP1 has a conserved function as FTIP1. NnFTIP1 and NnFT1 share similar tissue expression patterns and subcellular localization. NnFTIP1 and NnFT1 interact both in vitro and in vivo. In addition, NnFTIP1 affects NnFT1 transport from leaves to the SAM. Furthermore, we found that NnUOF8, a MYB-like transcription factor, directly regulates the expression of NnFTIP1. Our results suggest that the functions of FTIP1 and FT are conserved during evolution in flowering plants.

Advances on Plant Ubiquitylome-From Mechanism to Application.

Post-translational modifications (PTMs) of proteins enable modulation of their structure, function, localization and turnover. To date, over 660 PTMs have been reported, among which, reversible PTMs are regarded as the key players in cellular signaling. Signaling mediated by PTMs is faster than re-initiation of gene expression, which may result in a faster response that is particularly crucial for plants due to their sessile nature. Ubiquitylation has been widely reported to be involved in many aspects of plant growth and development and it is largely determined by its target protein. It is therefore of high interest to explore new ubiquitylated proteins/sites to obtain new insights into its mechanism and functions. In the last decades, extensive protein profiling of ubiquitylation has been achieved in different plants due to the advancement in ubiquitylated proteins (or peptides) affinity and mass spectrometry techniques. This obtained information on a large number of ubiquitylated proteins/sites helps crack the mechanism of ubiquitylation in plants. In this review, we have summarized the latest advances in protein ubiquitylation to gain comprehensive and updated knowledge in this field. Besides, the current and future challenges and barriers are also reviewed and discussed.

Ancient microRNA families that regulate transcription factors are preferentially preserved during plant radiation.

Essential genes are usually less likely to be lost during evolution, whereas dispensable genes are lost more frequently. Integrating sacred lotus and other plant microRNA (miRNA) data, we found different ancient miRNA families that arose before eudicot radiation exhibit different evolutionary trajectories. Those ancient miRNA families with higher copy and target numbers, and older age are more likely to be retained in plant descendants and more conserved in (hairpin-structured) miRNA gene sequences. Interestingly, a large portion of the well conserved miRNA families in plant lineages can target transcription factors (TFs). Also, we found miRNA families that target TFs are preferentially retained after sacred lotus genome duplication. In this article, we provide some points to discuss why miRNA families that regulate TFs are more likely to be preserved in plants.

Induction and quantitative proteomic analysis of cell dedifferentiation during callus formation of lotus (Nelumbo nucifera Gaertn.spp. baijianlian).

Lotus is an aquatic plant with high nutritional, ornamental and medical values. Its callus formation is crucial for germplasm innovation by genetic transformation. In this study, embryogenic callus was successfully induced on appropriate medium using cotyledons at 12days after pollination as explants. To dissect cellular dedifferentiation and callus formation processes at the proteome level, cotyledons before and tissues from 10 to 20days after induction were sampled for shotgun proteomic analysis. By applying multivariate statistics 91 proteins were detected as differentially regulated, and sorted into 6 functional groups according to MapMan ontology analysis. Most of these proteins were implicated in various metabolisms, demonstrating that plant cells underwent metabolism reprogramming during callus induction. 14.3% proteins were associated with stress and redox, indicating that the detached explants were subjected to a variety of stresses; 13.2% were cell and cell wall-related proteins, suggesting that these proteins played important roles in rapid cell division and proliferation. Some proteins were further evaluated at the mRNA levels by quantitative reverse transcription PCR analysis. In conclusion, the results contributed to further deciphering of molecular processes of cellular dedifferentiation and callus formation, and provided a reference data set for the establishment of transgenic transformation in lotus.

Reversing drug resistance of cisplatin by hsp90 inhibitors in human ovarian cancer cells.

OBJECTIVE: To investigate the mechanisms for reversing drug resistance of cisplatin (DDP) by Hsp90 inhibitors (geldanamycin (GA), 17-AAG, 17-DMAG) in human ovarian cancer. METHODS: Cell proliferation rate in DDP resistant human ovarian cancer cell line SKOV3/DDP and its parent cell line SKOV3 after treatment with Hsp90 inhibitors and/or DDP were tested by MTT assay, and the reversing fold (RF) of DDP by Hsp90 inhibitors was calculated. Cell cycle and cell apoptosis status after treatment were analyzed by flow cytometry. The expression of multiple drug resistance related genes was analyzed by RT-PCR and Western-blot. RESULTS: All three tested Hsp90 inhibitors synergistically inhibited the cell proliferation of SKOV3 with DDP and enhanced the sensitivity of SKOV3/DDP cells to DDP. The RF of DDP by Hsp90 inhibitors were all more than two fold. GA caused cell cycle arrest in G2/M phasein SKOV3 cells. 17-AAG increased cell apoptosis but did not change cell cycle in SKOV3/DDP cells. The mRNA and protein expression levels of various drug resistant related genes including LRP, GST-π, p53, bcl-2, survivin, ERCC1, XRCC1, BRCA1 and BRCA2 were more dramatically altered by Hsp90 inhibitors and DDP in combination compared to Hsp90 inhibitors or DDP treatment alone. CONCLUSIONS: Exposure of SKOV3/DDP cells to Hsp90 inhibitors and DDP in combination results in synergistic cytotoxic and pro-apoptotic effects. Hsp90 inhibitors reverse the drug resistance of SKOV3/DDP cells to DDP by modifying the expression of multiple drug resistance related genes.

Analysis of Flavonoids in Lotus (Nelumbo nucifera) Leaves and Their Antioxidant Activity Using Macroporous Resin Chromatography Coupled with LC-MS/MS and Antioxidant Biochemical Assays.

Lotus (Nelumbo nucifera) leaves, a traditional Chinese medicinal herb, are rich in flavonoids. In an effort to thoroughly analyze their flavonoid components, macroporous resin chromatography coupled with HPLC-MS/MS was employed to simultaneously enrich and identify flavonoids from lotus leaves. Flavonoids extracted from lotus leaves were selectively enriched in the macroporous resin column, eluted subsequently as fraction II, and successively subjected to analysis with the HPLC-MS/MS and bioactivity assays. Altogether, fourteen flavonoids were identified, four of which were identified from lotus leaves for the first time, including quercetin 3-O-rhamnopyranosyl-(1→2)-glucopyranoside, quercetin 3-O-arabinoside, diosmetin 7-O-hexose, and isorhamnetin 3-O-arabino- pyranosyl-(1→2)-glucopyranoside. Further bioactivity assays revealed that these flavonoids from lotus leaves possess strong antioxidant activity, and demonstrate very good potential to be explored as food supplements or even pharmaceutical products to improve human health.

The Cysteine2/Histidine2-Type Transcription Factor ZINC FINGER OF ARABIDOPSIS THALIANA6 Modulates Biotic and Abiotic Stress Responses by Activating Salicylic Acid-Related Genes and C-REPEAT-BINDING FACTOR Genes in Arabidopsis.

The cysteine2/histidine2-type zinc finger proteins are a large family of transcription regulators, and some of them play essential roles in plant responses to biotic and abiotic stress. In this study, we found that expression of C2H2-type ZINC FINGER OF ARABIDOPSIS THALIANA6 (AtZAT6) was transcriptionally induced by salt, dehydration, cold stress treatments, and pathogen infection, and AtZAT6 was predominantly located in the nucleus. AtZAT6-overexpressing plants exhibited improved resistance to pathogen infection, salt, drought, and freezing stresses, while AtZAT6 knockdown plants showed decreased stress resistance. AtZAT6 positively modulates expression levels of stress-related genes by directly binding to the TACAAT motifs in the promoter region of pathogen-related genes (ENHANCED DISEASE SUSCEPTIBILITY1, PHYTOALEXIN DEFICIENT4, PATHOGENESIS-RELATED GENE1 [PR1], PR2, and PR5) and abiotic stress-responsive genes (C-REPEAT-BINDING FACTOR1 [CBF1], CBF2, and CBF3). Moreover, overexpression of AtZAT6 exhibited pleiotrophic phenotypes with curly leaves and small-sized plant at vegetative stage and reduced size of floral organs and siliques at the reproductive stage. Modulation of AtZAT6 also positively regulates the accumulation of salicylic acid and reactive oxygen species (hydrogen peroxide and superoxide radical). Taken together, our findings indicated that AtZAT6 plays important roles in plant development and positively modulates biotic and abiotic stress resistance by activating the expression levels of salicylic acid-related genes and CBF genes.

Proteome analysis of peroxisomes from etiolated Arabidopsis seedlings identifies a peroxisomal protease involved in ß-oxidation and development.

Plant peroxisomes are highly dynamic organelles that mediate a suite of metabolic processes crucial to development. Peroxisomes in seeds/dark-grown seedlings and in photosynthetic tissues constitute two major subtypes of plant peroxisomes, which had been postulated to contain distinct primary biochemical properties. Multiple in-depth proteomic analyses had been performed on leaf peroxisomes, yet the major makeup of peroxisomes in seeds or dark-grown seedlings remained unclear. To compare the metabolic pathways of the two dominant plant peroxisomal subtypes and discover new peroxisomal proteins that function specifically during seed germination, we performed proteomic analysis of peroxisomes from etiolated Arabidopsis (Arabidopsis thaliana) seedlings. The detection of 77 peroxisomal proteins allowed us to perform comparative analysis with the peroxisomal proteome of green leaves, which revealed a large overlap between these two primary peroxisomal variants. Subcellular targeting analysis by fluorescence microscopy validated around 10 new peroxisomal proteins in Arabidopsis. Mutant analysis suggested the role of the cysteine protease RESPONSE TO DROUGHT21A-LIKE1 in ß-oxidation, seed germination, and growth. This work provides a much-needed road map of a major type of plant peroxisome and has established a basis for future investigations of peroxisomal proteolytic processes to understand their roles in development and in plant interaction with the environment.

Proteomic analysis of de-etiolated rice seedlings upon exposure to light.

Two-week-old dark-grown rice seedlings were de-etiolated upon exposure to light. A comparison of 2-DE protein profiles between the dark-grown control and the rice seedlings illuminated respectively for 6, 12 and 24 h revealed 52 differentially expressed CBB-stained spots. Of these changed spots, the identity of 51 protein spots was determined by MALDI-TOF MS. Of these identified proteins, 13 proteins were related to light reactions of photosynthesis, photosynthetic carbon assimilation and chlorophyll biosynthesis, indicating the complex process of biogenesis of photosynthetic apparatus was correlated to the transition from a dark-grown (etiolated) to a light-grown (de-etiolated) morphology. In addition, three proteins related to antioxidation and detoxification decreased in de-etiolated rice seedlings implied, that the etiolated rice seedlings possibly be under an oxidative stress which could be released during their early stages of de-etiolation. The increase of S-adenosylmethionine synthetase that is involved in the biosynthesis of the phytohormone ethylene might contribute to the phenotypic development of the apical hook in the de-etiolated rice seedlings. These results yield a comprehensive picture of the post-transcriptional response for de-etiolation of rice seedlings and serve as a basic platform for further characterization of gene function and regulation in light-induced development of plants.