Directly transforming PCR-amplified DNA fragments into plant cells is a versatile system that facilitates the transient expression assay

Complex plant responses to drought and heat stress under climate change

Global climate change is predicted to result in increased yield losses of agricultural crops caused by environmental conditions. In particular, heat and drought stress are major factors that negatively affect plant development and reproduction, and previous studies have revealed how these stresses induce plant responses at physiological and molecular levels. Here, we provide a comprehensive overview of current knowledge concerning how drought, heat, and combinations of these stress conditions affect the status of plants, including crops, by affecting factors such as stomatal conductance, photosynthetic activity, cellular oxidative conditions, metabolomic profiles, and molecular signaling mechanisms. We further discuss stress-responsive regulatory factors such as transcription factors and signaling factors, which play critical roles in adaptation to both drought and heat stress conditions and potentially function as 'hubs' in drought and/or heat stress responses. Additionally, we present recent findings based on forward genetic approaches that reveal natural variations in agricultural crops that play critical roles in agricultural traits under drought and/or heat conditions. Finally, we provide an overview of the application of decades of study results to actual agricultural fields as a strategy to increase drought and/or heat stress tolerance. This review summarizes our current understanding of plant responses to drought, heat, and combinations of these stress conditions.

Novel markers for high-throughput protoplast-based analyses of phytohormone signaling

Phytohormones mediate most diverse processes in plants, ranging from organ development to immune responses. Receptor protein complexes perceive changes in intracellular phytohormone levels and trigger a signaling cascade to effectuate downstream responses. The in planta analysis of elements involved in phytohormone signaling can be achieved through transient expression in mesophyll protoplasts, which are a fast and versatile alternative to generating plant lines that stably express a transgene. While promoter-reporter constructs have been used successfully to identify internal or external factors that change phytohormone signaling, the range of available marker constructs does not meet the potential of the protoplast technique for large scale approaches. The aim of our study was to provide novel markers for phytohormone signaling in the Arabidopsis mesophyll protoplast system. We validated 18 promoter::luciferase constructs towards their phytohormone responsiveness and specificity and suggest an experimental setup for high-throughput analyses. We recommend novel markers for the analysis of auxin, abscisic acid, cytokinin, salicylic acid and jasmonic acid responses that will facilitate future screens for biological elements and environmental stimuli affecting phytohormone signaling.

Functional efficiency of PCR vectors in vitro and at the organism level

The functional efficiency of the expression cassettes integrated into a plasmid and a PCR- amplified fragment was comparatively analyzed after transient transfection in vitro or introduction into the developing embryo of Danio rerio. The cassettes contained the reporter genes, luciferase of Photinus pyralis (luc) or enhanced green fluorescent protein, under the control of the promoter of human cytomegalovirus immediate-early genes. In the in vitro system, the efficiency of the circular plasmid was 2.5 times higher than that of the PCR- amplified fragment. The effect of mutations in the expression cassette on the efficiency of the transgene expression in the PCR- amplified fragment was quantitatively evaluated. The mutations generated after 25 amplification cycles with Taq DNA polymerase decreased luciferase activity in transfected cells by 65–85%. Thus, mutations are the key factor of decreased functional efficiency of the PCR- amplified fragment relative to the circular plasmid in this experimental model, while other factors apparently have a lesser impact. At the organism level, no significant difference in the expression efficiency of the plasmid and PCR- amplified fragment has been revealed. Comparison of the vector efficiencies in in vivo and in vitro systems demonstrates that the level of luciferase in the D. rerio cell lysate, normalized to the molar concentration of the vector, is by three orders of magnitude higher than that after the cell transfection in vitro, which indicates that the quantitative data obtained for in vitro systems should not be directly extrapolated to the organism level.

Two SLENDER AND CRINKLY LEAF dioxygenases play an essential role in rice shoot development

It is clear that 2-oxoglutarate-dependent dioxygenases have critical functions in salicylic acid (SA) metabolism in plants, yet their role in SA biosynthesis is poorly understood. Here, we report that two dioxygenase-encoding genes, SLENDER AND CRINKLY LEAF1 (SLC1) and SLC2, play essential roles in shoot development and SA production in rice. Overexpression of SLC1 (SLC1-OE) or SLC2 (SLC2-OE) in rice produced infertile plants with slender and crinkly leaves. Disruption of SLC1 or SLC2 led to dwarf plants, while simultaneous down-regulation of SLC1 and SLC2 resulted in a severe defect in early leaf development. Enhanced SA levels in SLC1-OE plants and decreased SA levels in slc1 and slc2 mutants were observed. Accordingly, these lines all showed altered expression of a set of SA-related genes. We demonstrated that SLC1 interacts with homeobox1 (OSH1), and that either the knotted1-like homeobox (KNOX1) or glutamate, leucine, and lysine (ELK) domain of OSH1 is sufficient for accomplishing this interaction. Collectively, our data reveal the importance of SLC1 and SLC2 in rice shoot development.

Biolistic Approach for Transient Gene Expression Studies in Plants

Since its inception in the late 1980s, the delivery of exogenous nucleic acids into living cells via high-velocity microprojectiles (biolistic, or microparticle bombardment) has been an invaluable tool for both agricultural and fundamental plant research. Here, we review the technical aspects and the major applications of the biolistic method for studies involving transient gene expression in plant cells. These studies cover multiple areas of plant research, including gene expression, protein subcellular localization and cell-to-cell movement, plant virology, silencing, and the more recently developed targeted genome editing via transient expression of customized endonucleases.

Expression of maize calcium-dependent protein kinase (ZmCPK11) improves salt tolerance in transgenic Arabidopsis plants by regulating sodium and potassium homeostasis and stabilizing photosystem II

In plants, CALCIUM-DEPENDENT PROTEIN KINASES (CDPKs/CPKs) are involved in calcium signaling in response to endogenous and environmental stimuli. Here, we report that ZmCPK11, one of maize CDPKs, participates in salt stress response and tolerance. Salt stress induced expression and upregulated the activity of ZmCPK11 in maize roots and leaves. Activation of ZmCPK11 upon salt stress was also observed in roots and leaves of transgenic Arabidopsis plants expressing ZmCPK11. The transgenic plants showed a long-root phenotype under control conditions and a short-root phenotype under NaCl, abscisic acid (ABA) or jasmonic acid (JA) treatment. Analysis of ABA and JA content in roots indicated that ZmCPK11 can mediate root growth by regulating the levels of these phytohormones. Moreover, 4-week-old transgenic plants were more tolerant to salinity than the wild-type plants. Their leaves were less chlorotic and showed weaker symptoms of senescence accompanied by higher chlorophyll content and higher quantum efficiency of photosystem II. The expression of Na⁺ /K⁺ transporters (HKT1, SOS1 and NHX1) and transcription factors (CBF1, CBF2, CBF3, ZAT6 and ZAT10) with known links to salinity tolerance was upregulated in roots of the transgenic plants upon salt stress. Furthermore, the transgenic plants accumulated less Na⁺ in roots and leaves under salinity, and showed a higher K⁺ /Na⁺ ratio in leaves. These results show that the improved salt tolerance in ZmCPK11-transgenic plants could be due to an upregulation of genes involved in the maintenance of intracellular Na⁺ and K⁺ homeostasis and a protection of photosystem II against damage.

Properties and functions of calcium-dependent protein kinases and their relatives in Arabidopsis thaliana

Calcium is a ubiquitous second messenger that mediates plant responses to developmental and environmental cues. Calcium-dependent protein kinases (CDPKs) are key actors of plant signaling that convey calcium signals into physiological responses by phosphorylating various substrates including ion channels, transcription factors and metabolic enzymes. This large diversity of targets confers pivotal roles of CDPKs in shoot and root development, pollen tube growth, stomatal movements, hormonal signaling, transcriptional reprogramming and stress tolerance. On the one hand, specificity in CDPK signaling is achieved by differential calcium sensitivities, expression patterns, subcellular localizations and substrates. On the other hand, CDPKs also target some common substrates to ensure key cellular processes indispensable for plant growth and survival in adverse environmental conditions. In addition, the CDPK-related protein kinases (CRKs) might be closer to some CDPKs than previously anticipated and could contribute to calcium signaling despite their inability to bind calcium. This review highlights the regulatory properties of Arabidopsis CDPKs and CRKs that coordinate their multifaceted functions in development, immunity and abiotic stress responses.

OsMADS18, a membrane-bound MADS-box transcription factor, modulates plant architecture and the abscisic acid response in rice

The APETALA1 (AP1)/FRUITFULL (FUL)-like transcription factor OsMADS18 plays diverse functions in rice development, but the underlying molecular mechanisms are far from fully understood. Here, we report that down-regulation of OsMADS18 expression in RNAi lines caused a delay in seed germination and young seedling growth, whereas the overexpression of OsMADS18 produced plants with fewer tillers. In targeted OsMADS18 genome-edited mutants (osmads18-cas9), an increased number of tillers, altered panicle size, and reduced seed setting were observed. The EYFP-OsMADS18 (full-length) protein was localized to the nucleus and plasma membrane but the EYFP-OsMADS18-N (N-terminus) protein mainly localized to the nucleus. The expression of OsMADS18 could be stimulated by abscisic acid (ABA), and ABA stimulation triggered the cleavage of HA-OsMADS18 and the translocation of OsMADS18 from the plasma membrane to the nucleus. The inhibitory effect of ABA on seedling growth was less effective in the OsMADS18-overexpressing plants. The expression of a set of ABA-responsive genes was significantly reduced in the overexpressing plants. The phenotypes of transgenic plants expressing EYFP-OsMADS18-N resembled those observed in the osmads18-cas9 mutants. Analysis of the interaction of OsMADS18 with OsMADS14, OsMADS15, and OsMADS57 strongly suggests an essential role for OsMADS18 in rice development.

Drought and heat stress-related proteins: an update about their functional relevance in imparting stress tolerance in agricultural crops

We describe here the recent developments about the involvement of diverse stress-related proteins in sensing, signaling, and defending the cells in plants in response to drought or/and heat stress. In the current era of global climate drift, plant growth and productivity are often limited by various environmental stresses, especially drought and heat. Adaptation to abiotic stress is a multigenic process involving maintenance of homeostasis for proper survival under adverse environment. It has been widely observed that a series of proteins respond to heat and drought conditions at both transcriptional and translational levels. The proteins are involved in various signaling events, act as key transcriptional activators and saviors of plants under extreme environments. A detailed insight about the functional aspects of diverse stress-responsive proteins may assist in unraveling various stress resilience mechanisms in plants. Furthermore, by identifying the metabolic proteins associated with drought and heat tolerance, tolerant varieties can be produced through transgenic/recombinant technologies. A large number of regulatory and functional stress-associated proteins are reported to participate in response to heat and drought stresses, such as protein kinases, phosphatases, transcription factors, and late embryogenesis abundant proteins, dehydrins, osmotins, and heat shock proteins, which may be similar or unique to stress treatments. Few studies have revealed that cellular response to combined drought and heat stresses is distinctive, compared to their individual treatments. In this review, we would mainly focus on the new developments about various stress sensors and receptors, transcription factors, chaperones, and stress-associated proteins involved in drought or/and heat stresses, and their possible role in augmenting stress tolerance in crops.

Portoporator©: A portable low-cost electroporation device for gene transfer to cultured cells in biotechnology, biomedical research and education

Electroporation has been a widely established method for delivering DNA and other material into cells in vitro. Conventional electroporation infrastructure is typically immobile, non-customizable, non-transparent regarding the characteristics of output pulses, and expensive. Here, we describe a portable electroporator for DNA delivery into bacterial cells that can quickly be reconstructed using 3D desktop printing and off-the-shelf components. The device is light weight (700 g), small (70 × 180 × 210 mm) and extremely low-cost (<EUR 130). We provide the electrical circuitry and a detailed parts list for rebuilding the device. We characterize the properties of generated pulses and apply the system for gene delivery into bacterial Dh5α cells. We analyze the transformation efficiency based on the optical density of cell suspensions at 595 nm and on quantitative analysis of images obtained from bacterial cell-grown agar plates using colony forming units as well as confluence as indicators. We demonstrate time-dependency of the transformation efficiency using single pulses of 500 V between 1 and 1000 ms duration and we show that commercially available electroporation cuvettes of 1 mm gap size reveal higher transformation rates compared to cuvettes with 2 mm gap. We benchmark the transformation efficiency obtained using our platform with data from a heat shock-based transformation protocol and with data from a commercially available electroporator and show that our system reveals comparable results as the other techniques in the applied configurations. While this work focuses on genetic manipulation of bacterial cells, the device may also be applicable for delivery of genetic material small molecule or nanomaterials into other cell types, including mammalian cells.

Factores que afectan la expresión transitoria del gen GUS en yuca (Manihot esculenta Crantz)

La expresión transitoria es una métodología ampliamente utilizada para el estudio de genes. Sin embargo, hasta la fecha no existe un reporte en donde se utilice esta técnica en hojas de yuca de plantas adultas. Por esta razón este trabajo se centró en la determinación de algunos parámetros críticos para la expresión transitoria del gen GUS en yuca como son: la metodología para introducir la bacteria, la cepa de Agrobacterium, el tiempo post-inoculación, la introducción del gen VirG y la expresión del gen GUS en algunas variedades de yuca. Los resultados indicaron niveles más altos de expresión del gen GUS entre 5-7 días post-inoculación (dpi), agroinfiltrando con la cepa GV3101 y un incremento en la virulencia de esta cepa mediante la introducción del gen VirG. Por último se observaron diferentes niveles de expresión del gen GUS entre las variedades de yuca evaluadas, lo que indica que el factor genético es clave en la eficiencia de la agroinfiltración en este cultivo.

The dioxygenase GIM2 functions in seed germination by altering gibberellin production in Arabidopsis

The phytohormones gibberellic acid (GA) and abscisic acid (ABA) antagonistically control seed germination. High levels of GA favor seed germination, whereas high levels of ABA hinder this process. The direct relationship between GA biosynthesis and seed germination ability need further investigation. Here, we identified the ABA-insensitive gain-of-function mutant germination insensitive to ABA mutant 2 (gim2) by screening a population of XVE T-DNA-tagged mutant lines. Based on two loss-of-function gim2-ko mutant lines, the disruption of GIM2 function caused a delay in seed germination. By contrast, upregulation of GIM2 accelerated seed germination, as observed in transgenic lines overexpressing GIM2 (OE). We detected a reduction in endogenous bioactive GA levels and an increase in endogenous ABA levels in the gim2-ko mutants compared to wild type. Conversely, the OE lines had increased endogenous bioactive GA levels and decreased endogenous ABA levels. The expression levels of a set of GA- and/or ABA-related genes were altered in both the gim2-ko mutants and the OE lines. We confirmed that GIM2 has dioxygenase activity using an in vitro enzyme assay, observing that GIM2 can oxidize GA₁₂ . Hence, our characterization of GIM2 demonstrates that it plays a role in seed germination by affecting the GA metabolic pathway in Arabidopsis.

Revisiting paradigms of Ca2+ signaling protein kinase regulation in plants

Calcium (Ca2+) serves as a universal second messenger in eukaryotic signal transduction. Understanding the Ca2+ activation kinetics of Ca2+ sensors is critical to understanding the cellular signaling mechanisms involved. In this review, we discuss the regulatory properties of two sensor classes: the Ca2+-dependent protein kinases (CPKs/CDPKs) and the calcineurin B-like (CBL) proteins that control the activity of CBL-interacting protein kinases (CIPKs) and identify emerging topics and some foundational points that are not well established experimentally. Most plant CPKs are activated by physiologically relevant Ca2+ concentrations except for those with degenerate EF hands, and new results suggest that the Ca2+-dependence of kinase activation may be modulated by both protein–protein interactions and CPK autophosphorylation. Early results indicated that activation of plant CPKs by Ca2+ occurred by relief of autoinhibition. However, recent studies of protist CDPKs suggest that intramolecular interactions between CDPK domains contribute allosteric control to CDPK activation. Further studies are required to elucidate the mechanisms regulating plant CPKs. With CBL–CIPKs, the two major activation mechanisms are thought to be (i) binding of Ca2+-bound CBL to the CIPK and (ii) phosphorylation of residues in the CIPK activation loop. However, the relative importance of these two mechanisms in regulating CIPK activity is unclear. Furthermore, information detailing activation by physiologically relevant [Ca2+] is lacking, such that the paradigm of CBLs as Ca2+ sensors still requires critical, experimental validation. Developing models of CPK and CIPK regulation is essential to understand how these kinases mediate Ca2+ signaling and to the design of experiments to test function in vivo.

Arabidopsis inositol polyphosphate multikinase delays flowering time through mediating transcriptional activation of FLOWERING LOCUS C

Timely flowering is critical for successful reproduction and seed yield in plants. A diverse range of regulators have been found to control flowering time in response to environmental and endogenous signals. Among these regulators, FLOWERING LOCUS C (FLC) acts as a central repressor of floral transition by blocking the expression of flowering integrator genes. Here, we report that Arabidopsis inositol polyphosphate multikinase (AtIPK2β) functions in flowering time control by mediating transcriptional regulation of FLC at the chromatin level. The atipk2β mutant flowers earlier, and AtIPK2β overexpressing plants exhibit late-flowering phenotypes. Quantitative reverse transcription-PCR (qRT-PCR) revealed that AtIPK2β promotes FLC expression. We performed chromatin immunoprecipitation-qPCR (ChIP-qPCR) assays and found that AtIPK2β binds to FLC chromatin. Further analysis showed that AtIPK2β interacts with FVE, a key repressor required for epigenetic silencing of FLC. qRT-PCR, ChIP-qPCR, and genetic analysis demonstrated that AtIPK2β is involved in FVE-mediated transcriptional regulation of FLC by repressing the accumulation of FVE on FLC. Moreover, we found that AtIPK2β associates with HDA6, an interaction partner of FVE mediating FLC chromatin silencing, and attenuates HDA6 accumulation at the FLC locus. Taken together, these findings suggest that AtIPK2β negatively regulates flowering time by blocking chromatin silencing of FLC.

Rice Inositol Polyphosphate Kinase (OsIPK2) Directly Interacts with OsIAA11 to Regulate Lateral Root Formation

The plant hormone auxin controls many aspects of plant growth and development by promoting the degradation of Auxin/Indole-3-acetic acid (Aux/IAA) proteins. The domain II (DII) of Aux/IAA proteins is sufficient for eliciting the degradation by directly interacting with the auxin receptor F-box protein TIR1 to form a TIR1/AFBs-Aux/IAA complex in an auxin-dependent manner. However, the underlying mechanisms of fine-tuning Aux/IAA degradation by auxin stimuli remain to be elucidated. Here, we show that OsIPK2, a rice (Oryza sativa) inositol polyphosphate kinase, directly interacts with an Aux/IAA protein OsIAA11 to repress its degradation. In a rice protoplast transient expression system, the auxin-induced degradation of Myc-OsIAA11 fusion was delayed by co-expressed GFP-OsIPK2 proteins. Furthermore, expressing additional OsIPK2 or its N-terminal amino acid sequence enhanced the accumulation of OsIAA11 proteins in transgenic plants, which in turn caused defects in lateral root formation and auxin response. Taken together, we identify a novel co-factor of Aux/IAA in auxin signaling and demonstrate its role in regulating lateral root development.

Know where your clients are: subcellular localization and targets of calcium-dependent protein kinases

Calcium-dependent protein kinases (CDPKs) are at the forefront of decoding transient Ca(2+) signals into physiological responses. They play a pivotal role in many aspects of plant life starting from pollen tube growth, during plant development, and in stress response to senescence and cell death. At the cellular level, Ca(2+) signals have a distinct, narrow distribution, thus requiring a conjoined localization of the decoders. Accordingly, most CDPKs have a distinct subcellular distribution which enables them to 'sense' the local Ca(2+) concentration and to interact specifically with their targets. Here we present a comprehensive overview of identified CDPK targets and discuss them in the context of kinase-substrate specificity and subcellular distribution of the CDPKs. This is particularly relevant for calcium-mediated phosphorylation where different CDPKs, as well as other kinases, were frequently reported to be involved in the regulation of the same target. However, often these studies were not performed in an in situ context. Thus, considering the specific expression patterns, distinct subcellular distribution, and different Ca(2+) affinities of CDPKs will narrow down the number of potential CDPKs for one given target. A number of aspects still remain unresolved, giving rise to pending questions for future research.

Calcium Sensors as Key Hubs in Plant Responses to Biotic and Abiotic Stresses

The Ca(2+) ion is recognized as a crucial second messenger in signaling pathways coupling the perception of environmental stimuli to plant adaptive responses. Indeed, one of the earliest events following the perception of environmental changes (temperature, salt stress, drought, pathogen, or herbivore attack) is intracellular variation of free calcium concentrations. These calcium variations differ in their spatio-temporal characteristics (subcellular location, amplitude, kinetics) with the nature and strength of the stimulus and, for this reason, they are considered as signatures encrypting information from the initial stimulus. This information is believed to drive a specific response by decoding via calcium-binding proteins. Based on recent examples, we illustrate how individual calcium sensors from the calcium-dependent protein kinase and calmodulin-like protein families can integrate inputs from various environmental changes. Focusing on members of these two families, shown to be involved in plant responses to both abiotic and biotic stimuli, we discuss their role as key hubs and we put forward hypotheses explaining how they can drive the signaling pathways toward the appropriate plant responses.

Major latex protein-like protein 43 (MLP43) functions as a positive regulator during abscisic acid responses and confers drought tolerance in Arabidopsis thaliana

Drought stress is one of the disadvantageous environmental conditions for plant growth and reproduction. Given the importance of abscisic acid (ABA) to plant growth and abiotic stress responses, identification of novel components involved in ABA signalling transduction is critical. In this study, we screened numerous Arabidopsis thaliana mutants by seed germination assay and identified a mutant mlp43 (major latex protein-like 43) with decreased ABA sensitivity in seed germination. The mlp43 mutant was sensitive to drought stress while the MLP43-overexpressed transgenic plants were drought tolerant. The tissue-specific expression pattern analysis showed that MLP43 was predominantly expressed in cotyledons, primary roots and apical meristems, and a subcellular localization study indicated that MLP43 was localized in the nucleus and cytoplasm. Physiological and biochemical analyses indicated that MLP43 functioned as a positive regulator in ABA- and drought-stress responses in Arabidopsis through regulating water loss efficiency, electrolyte leakage, ROS levels, and as well as ABA-responsive gene expression. Moreover, metabolite profiling analysis indicated that MLP43 could modulate the production of primary metabolites under drought stress conditions. Reconstitution of ABA signalling components in Arabidopsis protoplasts indicated that MLP43 was involved in ABA signalling transduction and acted upstream of SnRK2s by directly interacting with SnRK2.6 and ABF1 in a yeast two-hybrid assay. Moreover, ABA and drought stress down-regulated MLP43 expression as a negative feedback loop regulation to the performance of MLP43 in ABA and drought stress responses. Therefore, this study provided new insights for interpretation of physiological and molecular mechanisms of Arabidopsis MLP43 mediating ABA signalling transduction and drought stress responses.

Novel Synthetic Promoters from the Cestrum Yellow Leaf Curling Virus

Constitutive promoters direct gene expression uniformly in most tissues and cells at all stages of plant growth and development; they confer steady levels of transgene expression in plant cells and hence their demand is high in plant biology. The gene silencing due to promoter homology can be avoided by either using diverse promoters isolated from different plant and viral genomes or by designing synthetic promoters. The aim of this chapter was to describe the basic protocols needed to develop and analyze novel, synthetic, nearly constitutive promoters from Cestrum yellow leaf curling virus (CmYLCV) through promoter/leader deletion and activating cis-sequence analysis. We also describe the methods to evaluate the strength of the promoters efficiently in various transient expression systems like agroinfiltration assay, gene-gun method, and assay in tobacco protoplasts. Besides, the detailed methods for developing transgenic plants (tobacco and Arabidopsis) for evaluation of the promoter using the GUS reporter gene are also described. The detailed procedure for electrophoretic mobility shift assay (EMSA) coupled with super-shift EMSA analysis are also described for showing the binding of tobacco transcription factor, TGA1a to cis-elements in the CmYLCV distal promoter region.

Upregulation of ULK1 expression in PC-3 cells following tumor protein P53 transfection by sonoporation

The aim of the present study was to investigate whether ultrasound combined with microbubbles was able to enhance liposome-mediated transfection of genes into human prostate cancer cells, and to examine the association between autophagy and tumor protein P53 (P53). An MTT assay was used to evaluate cell viability, while flow cytometry and fluorescence microscopy were used to measure gene transfection efficiency. Autophagy was observed using transmission electron microscopy. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis were used to assess the expression of autophagy-associated genes. The results of the present study revealed that cell viability was significantly reduced following successfully enhanced transfection of P53 by ultrasound combined with microbubbles. In addition, serine/threonine-protein kinase ULK1 levels were simultaneously upregulated. Castration-resistant prostate cancer is difficult to treat and is investigated in the present study. P53 has a significant role in a number of key biological functions, including DNA repair, apoptosis, cell cycle, autophagy, senescence and angiogenesis. Prior to the present study, to the best of our knowledge, increased transfection efficiency and reduced side effects have been difficult to achieve. Ultrasound is considered to be a 'gentle' technique that may be able to achieve increased transfection efficiency and reduced side effects. The results of the present study highlight a potential novel therapeutic strategy for the treatment of prostate cancer.

Transient transformation meets gene function discovery: the strawberry fruit case

Beside the well known nutritional and health benefits, strawberry (FragariaXananassa) crop draws increasing attention as plant model system for the Rosaceae family, due to the short generation time, the rapid in vitro regeneration, and to the availability of the genome sequence of F.Xananassa and F. vesca species. In the last years, the use of high-throughput sequence technologies provided large amounts of molecular information on the genes possibly related to several biological processes of this crop. Nevertheless, the function of most genes or gene products is still poorly understood and needs investigation. Transient transformation technology provides a powerful tool to study gene function in vivo, avoiding difficult drawbacks that typically affect the stable transformation protocols, such as transformation efficiency, transformants selection, and regeneration. In this review we provide an overview of the use of transient expression in the investigation of the function of genes important for strawberry fruit development, defense and nutritional properties. The technical aspects related to an efficient use of this technique are described, and the possible impact and application in strawberry crop improvement are discussed.

Comparative analysis of synthetic DNA promoters for high-level gene expression in plants

MAIN CONCLUSION

We have designed two near- constitutive and stress-inducible promoters (CmYLCV9.11 and CmYLCV4); those are highly efficient in both dicot and monocot plants and have prospective to substitute the CaMV 35S promoter. We performed structural and functional studies of the full-length transcript promoter from Cestrum yellow leaf curling virus (CmYLCV) employing promoter/leader deletion and activating cis-sequence analysis. We designed a 465-bp long CmYLCV9.11 promoter fragment (-329 to +137 from transcription start site) that showed enhanced promoter activity and was highly responsive to both biotic and abiotic stresses. The CmYLCV9.11 promoter was about 28-fold stronger than the CaMV35S promoter in transient and stable transgenic assays using β-glucuronidase (GUS) reporter gene. The CmYLCV9.11 promoter also demonstrated stronger activity than the previously reported CmYLCV promoter fragments, CmpC (-341 to +5) and CmpS (-349 to +59) in transient systems like maize protoplasts and onion epidermal cells as well as transgenic systems. A good correlation between CmYLCV9.11 promoter-driven GUS-accumulation/enzymatic activities with corresponding uidA-mRNA level in transgenic tobacco plants was shown. Histochemical (X-Gluc) staining of transgenic seedlings, root and floral parts expressing the GUS under the control of CmYLCV9.11, CaMV35S, CmpC and CmpS promoters also support the above findings. The CmYLCV9.11 promoter is a constitutive promoter and the expression level in tissues of transgenic tobacco plants was in the following order: root > leaf > stem. The tobacco transcription factor TGA1a was found to bind strongly to the CmYLCV9.11 promoter region, as shown by Gel-shift assay and South-Western blot analysis. In addition, the CmYLCV9.11 promoter was regulated by a number of abiotic and biotic stresses as studied in transgenic Arabidopsis and tobacco plants. The newly derived CmYLCV9.11 promoter is an efficient tool for biotechnological applications.

Overexpression of OsKTN80a, a katanin P80 ortholog, caused the repressed cell elongation and stalled cell division mediated by microtubule apparatus defects in primary root in Oryza sativa

Katanin, a microtubule-severing enzyme, consists of two subunits: the catalytic subunit P60, and the regulatory subunit P80. In several species, P80 functions in meiotic spindle organization, the flagella biogenesis, the neuronal development, and the male gamete production. However, the P80 function in higher plants remains elusive. In this study, we found that there are three katanin P80 orthologs (OsKTN80a, OsKTN80b, and OsKTN80c) in Oryza sativa L. Overexpression of OsKTN80a caused the retarded root growth of rice seedlings. Further investigation indicates that the retained root growth was caused by the repressed cell elongation in the elongation zone and the stalled cytokinesis in the division zone in the root tip. The in vivo examination suggests that OsKTN80a acts as a microtubule stabilizer. We prove that OsKTN80a, possibly associated with OsKTN60, is involved in root growth via regulating the cell elongation and division.

pSiM24 is a novel versatile gene expression vector for transient assays as well as stable expression of foreign genes in plants

We have constructed a small and highly efficient binary Ti vector pSiM24 for plant transformation with maximum efficacy. In the pSiM24 vector, the size of the backbone of the early binary vector pKYLXM24 (GenBank Accession No. HM036220; a derivative of pKYLX71) was reduced from 12.8 kb to 7.1 kb. The binary vector pSiM24 is composed of the following genetic elements: left and right T-DNA borders, a modified full-length transcript promoter (M24) of Mirabilis mosaic virus with duplicated enhancer domains, three multiple cloning sites, a 3'rbcsE9 terminator, replication functions for Escherichia coli (ColE1) and Agrobacterium tumefaciens (pRK2-OriV) and the replicase trfA gene, selectable marker genes for kanamycin resistance (nptII) and ampicillin resistance (bla). The pSiM24 plasmid offers a wide selection of cloning sites, high copy numbers in E. coli and a high cloning capacity for easily manipulating different genetic elements. It has been fully tested in transferring transgenes such as green fluorescent protein (GFP) and β-glucuronidase (GUS) both transiently (agro-infiltration, protoplast electroporation and biolistic) and stably in plant systems (Arabidopsis and tobacco) using both agrobacterium-mediated transformation and biolistic procedures. Not only reporter genes, several other introduced genes were also effectively expressed using pSiM24 expression vector. Hence, the pSiM24 vector would be useful for various plant biotechnological applications. In addition, the pSiM24 plasmid can act as a platform for other applications, such as gene expression studies and different promoter expressional analyses.

High-efficiency nuclear transformation of the oleaginous marine Nannochloropsis species using PCR product

Nannochloropsis are model species for investigating biofuel production by algae. To develop them into an integrated photons-to-fuel production platform, high efficiency transformation methods are necessary. Here, we obtained the β-tubulin promoter regions of all recognized species of genus Nannochloropsis, and successfully transformed all five marine species by electroporation. In addition, the PCR amplified double stranded DNA fragments (PCR fragments) based transformation system was established in these Nannochloropsis species, which showed much higher transformation efficiency (10.7–61.2 × 10−6, 1.5–13-fold) than that of linearized plasmid based transformation. The cotransformation of N. salina using a circular plasmid containing a non-selectable GUS gene and a PCR fragment containing only a selection marker cassette was also achieved and found to be very efficient (over 50%). This simple and highly efficient transformation protocol reported in our study provided a useful tool for gene functional analysis and genetic engineering of the oleaginous Nannochloropsis species.

Calcium-dependent protein kinases: hubs in plant stress signaling and development

These kinases are identified as integrators in plant signaling, with distinct as well as shared phosphorylation substrates mediating pathway specificity.