Heat stress can cause severe crop yield losses by impairing reproductive development. However, the underlying mechanisms are poorly understood. We examined patterns of carbon allocation and activities of sucrose cleavage enzymes in heat-tolerant (HT) and -sensitive (HS) tomato (Solanum lycopersicum L.) lines subjected to normal (control) and heat stress temperatures. At the control temperature of 25/20 °C (day/night) the HT line exhibited higher cell wall invertase (CWIN) activity in flowers and young fruits and partitioned more sucrose to fruits but less to vegetative tissues as compared to the HS line, independent of leaf photosynthetic capacity. Upon 2-, 4-, or 24-h exposure to day or night temperatures of 5 °C or more above 25/20 °C, cell wall (CWIN) and vacuolar invertases (VIN), but not sucrose synthase (SuSy), activities in young fruit of the HT line were significantly higher than those of the HS line. The HT line had a higher level of transcript of a CWIN gene, Lin7, in 5-day fruit than the HS line under control and heat stress temperatures. Interestingly, heat induced transcription of an invertase inhibitor gene, INVINH1, but reduced its protein abundance. Transcript levels of LePLDa1, encoding phospholipase D, which degrades cell membranes, was less in the HT line than in the HS line after exposure to heat stress. The data indicate that high invertase activity of, and increased sucrose import into, young tomato fruit could contribute to their heat tolerance through increasing sink strength and sugar signalling activities, possibly regulating a programmed cell death pathway.

There are currently a number of imaging techniques available for evaluating the morphology of liposomes and other nanoparticles, with each having its own advantages and disadvantages that should be considered when interpreting data. Controlling and validating the morphology of nanoparticles is of key importance for the effective clinical translation of liposomal formulations. There are a number of physical characteristics of liposomes that determine their in vivo behavior, including size, surface characteristics, lamellarity, and homogeneity. Despite the great importance of the morphology of nanoparticles, it is generally not well-characterized and is difficult to control. Appropriate imaging techniques provide important details regarding the morphological characteristics of nanoparticles, and should be used in conjunction with other methods to assess physicochemical parameters. In this review, we will discuss the advantages and limitations of available imaging techniques used to evaluate liposomal formulations.

Nanomedicines are typically submicrometer-sized carrier materials (nanoparticles) encapsulating therapeutic and/or imaging compounds that are used for the prevention, diagnosis and treatment of diseases. They are increasingly being used to overcome biological barriers in the body to improve the way we deliver compounds to specific tissues and organs. Nanomedicine technology aims to improve the balance between the efficacy and the toxicity of therapeutic compounds. Nanoparticles, one of the key technologies of nanomedicine, can exhibit a combination of physical, chemical and biological characteristics that determine their in vivo behavior. A key component in the translational assessment of nanomedicines is determining the biodistribution of the nanoparticles following in vivo administration in animals and humans. There are a range of techniques available for evaluating nanoparticle biodistribution, including histology, electron microscopy, liquid scintillation counting (LSC), indirectly measuring drug concentrations, in vivo optical imaging, computed tomography (CT), magnetic resonance imaging (MRI), and nuclear medicine imaging. Each technique has its own advantages and limitations, as well as capabilities for assessing real-time, whole-organ and cellular accumulation. This review will address the principles and methodology of each technique and their advantages and limitations for evaluating in vivo biodistribution of nanoparticles.

BackgroundRecently, there has been interest in establishing a monocot C4 model species with a small genome, short lifecycle, and capacity for genetic transformation. Setaria viridis has been adopted to fill this role, since reports of Agrobacterium-mediated transformation in 2010, and sequencing of its genome in 2012. To date, S. viridis has primarily been used to further our understanding of C4 photosynthesis, but is also an ideal system for the study of biomass crops, which are almost exclusively C4 panicoid grasses. Biogenesis of stem tissue, its cell wall composition, and soluble sugar content are important determinants of bioenergy crop yields. Here we show that a developing S. viridis internode is a valuable experimental system for gene discovery in relation to these important bioenergy feedstock traits.ResultsThe rate of maximal stem biomass accumulation in S. viridis A10 under long day growth was at the half-head emergence developmental stage. At this stage of development, internode 5 (of 7) was found to be rapidly expanding with an active meristem, a zone of cell expansion (primary cell walls), a transitional zone where cell expansion ceased and secondary cell wall deposition was initiated, and a mature zone that was actively accumulating soluble sugars. A simple method for identifying these zones was established allowing rapid dissection and snap-freezing for RNAseq analysis. A transcriptome profile was generated for each zone showing a transition from cell division and nucleic acid synthesis/processing in the meristem, to metabolism, energy synthesis, and primary cell wall synthesis in the cell expansion zone, to secondary cell wall synthesis in the transitional zone, to sugar transport, and photosynthesis in the mature zone.ConclusionThe identification of these zones has provided a valuable experimental system for investigating key bioenergy traits, including meristematic activity, cell wall biosynthesis, and soluble sugar accumulation, in a C4 panicoid grass that has genetic resources, a short life cycle, and small stature allowing controlled experimental conditions in growth cabinets. Here we have presented a comprehensive map of gene expression and metabolites in this experimental system to facilitate gene discovery and controlled hypothesis testing for bioenergy research in S. viridis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0457-6) contains supplementary material, which is available to authorized users.

Central to understanding fruit development is to elucidate the processes mediating a successful transition from pre-pollination ovaries to newly set fruit, a key step in establishing fruit yield potential. In tomato, cell wall invertase (CWIN) LIN5 and its inhibitor INH1 are essential for fruit growth. However, the molecular and cellular basis by which they exert their roles in ovary-to-fruit transition remains unknown. To address this issue, we conducted a study focusing on ovaries and fruitlets at 2 days before and 2 days after anthesis, respectively. In situ hybridization analyses revealed that LIN5 and INH1 exhibited a dispersed expression in ovaries compared with their phloem-specific expression in fruitlets. Remarkably, LIN5 and INH1 proteins were immunologically co-localized to cell walls of sieve elements (SEs) in ovaries immediately prior to anthesis and in young fruitlets, but were undetectable in provascular bundles of younger ovaries. A burst in CWIN activity occurred during ovary-to-fruit transition. Interestingly, the ovaries, but not the fruitlets, exhibited high expression of a defective invertase, SldeCWIN1, an ortholog of which is known to enhance inhibition of INH on CWIN activity in tobacco. Imaging of a fluorescent symplasmic tracer indicated an apoplasmic phloem unloading pathway operated in ovaries, contrary to the previously observed symplasmic unloading pathway in fruit pericarp. These new data indicate that (1) a phloem-specific patterning of the CWIN and INH mRNAs is induced during ovary-to-fruit transition, and (2) LIN5 protein functions specifically in walls of SEs and increases its activity during ovary-to-fruit transition, probably to facilitate phloem unloading and to generate a glucose signal positively regulating cell division, hence fruit set.