The essential roles of TGFB1 in reproduction

Transforming growth factor beta 1 (TGFB1) is implicated as a key regulator of the development and cyclic remodelling characteristic of reproductive tissues. The physiological significance of TGFB1 in reproductive biology and fertility has been extensively examined in Tgfb1 null mutant mice. Genetic deficiency in TGFB1 causes perturbed functioning of the hypothalamic–pituitary–gonadal axis, inhibiting luteinising hormone (LH) synthesis and leading to downstream effects on testosterone production in males and estrous cycle abnormalities in females. Oocyte developmental incompetence, accompanied by early embryo arrest as well as altered pubertal mammary gland morphogenesis are observed. In addition to LH and testosterone deficiency, male Tgfb1 null mice demonstrate complete inability to mate with females, associated with failure to initiate and/or sustain successful penile intromission or ejaculation. These studies demonstrate the profound significance of TGFB1 in male and female reproductive physiology, and provide a foundation for exploring the significance of this cytokine in human infertility and sexual dysfunction.     

Targeting molecular interactions essential for Plasmodium sexual reproduction

Malaria remains one of the most devastating infectious diseases, killing up to a million people every year. Whereas much progress has been made in understanding the life cycle of the parasite in the human host and in the mosquito vector, significant gaps of knowledge remain. Fertilization of malaria parasites, a process that takes place in the lumen of the mosquito midgut, is poorly understood and the molecular interactions (receptor–ligand) required for Plasmodium fertilization remain elusive. By use of a phage display library, we identified FG1 (Female Gamete peptide 1), a peptide that binds specifically to the surface of female Plasmodium berghei gametes. Importantly, FG1 but not a scrambled version of the peptide, strongly reduces P. berghei oocyst formation by interfering with fertilization. In addition, FG1 also inhibits P. falciparum oocyst formation suggesting that the peptide binds to a molecule on the surface of the female gamete whose structure is conserved. Identification of the molecular interactions disrupted by the FG1 peptide may lead to the development of novel malaria transmission‐blocking strategies.     

Copper nutrition of wheat in relation to nitrogen and phosphorus fertilization

Summary In a pot culture study, copper addition to soil increased the crop yield only in presence of nitrogen. The latter increased the utilization of both native as well as applied copper but more that of applied. It also minimised the adverse effect of applied phosphorus on copper utilization. Phosphorus at the rate 45 ppm had the tendency of decreasing copper uptake by wheat if applied without nitrogen or with its low level.     

Identification of a threshold level to assess essential derivation in durum wheat

Essentially derived varieties (EDV) are considered to be those that are obtained from an original variety by means of methods that do not substantially modify its genetic structure, and whose characteristics are therefore derived from the original. The identification of EDV requires the definition of a threshold value of genetic similarity between the new and the original variety that if exceeded would suggest derivation. Although protocols for estimating genetic similarities based on molecular markers have been proposed for EDV identification in some species, no information was available for durum wheat (Triticum durum). A set of 60 genotypes (F8 or F9 lines and their parents) representing different levels of relatedness were profiled using 14 (later reduced to 13 by excluding the most deviant one) amplified fragment length polymorphism (AFLP) primer combinations and 109 simple sequence repeat (SSR) loci evenly distributed in the genome. For both marker types, an EDV threshold was calculated according to the “tail principle” on the distributions of Jaccard similarities among the subset of 39 independent genotypes. For all pairs of closely related lines branched in advanced generations (F7–F8), or for all but one pairs of lines deriving from the same F4 family, similarities exceeded the thresholds for both marker types, indicating a very good agreement in showing cases of suspected derivation. Compared to SSR markers, AFLP markers appear more suitable for assessing essential derivation because of their superior cost-efficiency. Based on 13 AFLP primer combinations, a threshold of 0.96 Jaccard similarity is proposed, below which a variety should be considered to be independently derived.     

Vitellogenin 1 is essential for fish reproduction by transporting DHA-containing phosphatidylcholine from liver to ovary

Vitellogenins (Vtgs) are essential for female reproduction in oviparous animals, yet the exact roles and mechanisms remain unknown. In the present study, we knocked out vtg1, which is the most abundant Vtg in zebrafish, Danio rerio via the CRISPR/Cas 9 technology. We aimed to identify the roles of Vtg1 and related mechanisms in reproduction and development. We found that, the Vtg1-deficient female zebrafish reduced gonadosomatic index, egg production, yolk granules and mature follicles in ovary compared to the wide type (WT). Moreover, the Vtg1-deficient zebrafish diminished hatching rates, cumulative survival rate, swimming capacity and food intake, but increased malformation rate, and delayed swim bladder development during embryo and early-larval phases. The Vtg1-deficiency in female broodstock inhibited docosahexaenoic acid-enriched phosphatidylcholine (DHA-PC) transportation from liver to ovary, which lowered DHA-PC content in ovary and offspring during larval stage. However, the Vtg1-deficient zebrafish increased gradually the total DHA-PC content via exogeneous food intake, and the differences in swimming capacity and food intake returned to normal as they matured. Furthermore, supplementing Vtg1-deficient zebrafish with dietary PC and DHA partly ameliorated the impaired female reproductive capacity and larval development during early phases. This study indicates that, DHA and PC carried by Vtg1 are crucial for female fecundity, and affect embryo and larval development through maternal-nutrition effects. This is the first study elucidating the nutrient and physiological functions of Vtg1 and the underlying biochemical mechanisms in fish reproduction and development.     

Impaired reproduction in three-spined sticklebacks exposed to ethinyl estradiol as juveniles

To investigate the population-level effects of exposure to environmental endocrine disrupters, a mesocosm-scale study was carried out in which the reproductive performance of groups of free-spawning three-spined sticklebacks, Gasterosteus aculeatus, exposed as juveniles to a model estrogen, was assessed. Juvenile sticklebacks were exposed to ethinyl estradiol (EE(2)) at measured concentrations of (mean +/- SEM) 1.75 +/- 0.37 ng L(-1) and 27.7 +/- 1.08 ng L(-1) for 4 wk posthatch and then reared thereafter in pristine lake water until they reached adulthood. Exposure to the higher EE(2) concentration resulted in the occurrence of ovotestis among males, whereas no gonadal abnormalities were evident among males exposed to the lower concentration of EE(2). In addition, when spawning was allowed in the mesocosm environment, fewer nests were built per male, and fewer eggs were deposited per nest, in the group exposed to 27.7 ng L(-1). Males from this group also exhibited a less intense nuptial coloration than control males. In the group exposed to 1.75 ng L(-1) EE(2) posthatch, significantly fewer nests were built than in the control group. These results demonstrate that the timing of exposure to estrogenic contaminants, in developmental terms, is critically important. Short-term exposure to estrogens as juveniles can clearly influence reproductive performance as adults, despite all growth and development subsequent to the exposure period taking place in an estrogen-free environment. In addition, these results suggest that reproductive dysfunction can occur even in fish with no gross abnormalities in gonadal structure. This suggests that the absence of gonadal intersex is not a reliable indicator of the reproductive potential, or estrogen-exposure history, of fish populations or the only important factor involved in compromising the reproduction of estrogen-exposed fish.     

Increased susceptibility to oxidative stress as a proximate cost of reproduction

In iteroparous species high investment in current reproduction is usually paid in terms of reduced future reproduction and increased mortality. However, the proximal mechanisms of these costs remain poorly understood. Free radicals arising as by‐products of normal metabolic activities have deleterious effects on cellular proteins, lipids and DNA, and this phenomenon is known as oxidative stress. Since reproduction is an energetically demanding activity, which increases both basal and field metabolic rates, one could expect that breeding effort generates an oxidative stress whose strength depends on the availability and efficiency of antioxidant defences. In agreement with this prediction, we show here for the first time that reproduction decreases antioxidant defences, illustrating that oxidative stress represents a cost of reproduction. We suggest that increased susceptibility to oxidative stress might be a general proximal connection between reproduction and survival underlying other mechanistic links previously acknowledged.     

Copper uptake kinetics in hydroponically-grown durum wheat (Triticum turgidum durum L.) as compared with soil’s ability to supply copper

This paper focuses on the causes of zonation on agricultural land affected by secondary salinity between two halophytic grasses, puccinellia (Puccinellia ciliata Bor. cv. Menemen) and tall wheatgrass (Thinopyrum ponticum (Podp.) Z.-W. Liu & R.R.-C. Wang cv. Tyrrell). We hypothesized that the differences in zonation of puccinellia and tall wheatgrass were caused primarily by differences in the tolerance of these two species to waterlogging under saline conditions. This hypothesis was tested by conducting experiments in the field and in the glasshouse in irrigated sand cultures. At a saltland field site, locations dominated by puccinellia had EC_e values that were consistently higher (11–12 dS/m in early spring, and 5–9 dS/m in late summer) than locations dominated by tall wheatgrass. However locations dominated by puccinellia also had a watertable that was shallower (0.07–0.09 m in the high rainfall season; 0.11–0.13 m in the low rainfall season) than locations dominated by tall wheatgrass. In the glasshouse both species had similar growth responses to salinity under drained conditions, with a 50% decrease in shoot dry mass (DM) at ～300 mM NaCl. However, the combination of salinity (250 mM NaCl) and waterlogging increased puccinellia shoot DM by 150% but decreased shoot DM of tall wheatgrass by 90% (compared with salinity alone). Under saline/waterlogged conditions, puccinellia showed better exclusion of Na⁺ and maintenance of K⁺/Na⁺ in the shoots than tall wheatgrass. We conclude that the zonation of puccinellia and tall wheatgrass is associated with differences in their ion regulation which leads to substantial differences in their growth under saline/waterlogged conditions.     

Seed P-enrichment as an effective P supply to wheat

Most fertilizer phosphorus (P) is sorbed by soil rather than being taken up by crops. We hypothesize enriching wheat seed with P before sowing the crop will reduce requirement of fertilizer P for subsequent wheat production. We produced P-enriched wheat (Triticum aestivum L.) seed by soaking the seed in different concentrations of potassium phosphate solution. We found that ~0.35 M potassium phosphate was the most effective concentration for P-enrichment of the seed. In pot and field experiments we found that the P-enriched seed required ~60% less fertilizer P than seed not soaked with potassium phosphate before sowing. Increases in shoot P content could not be explained only by the increase of seed P-enrichment, suggesting that P acquisition from soil was also enhanced. Under hydroponic conditions we found that root length was greater in seedlings grown from P-enriched seed with higher specific root length than in seedlings grown from non-P-enriched seed. We conclude P-enrichment of wheat seed before sowing reduces fertilizer P requirements of plants.     

Copper chaperone antioxidant protein1 is essential for copper homeostasis

Copper (Cu) is essential for plant growth but toxic in excess. Specific molecular mechanisms maintain Cu homeostasis to facilitate its use and avoid the toxicity. Cu chaperones, proteins containing a Cu-binding domain(s), are thought to assist Cu intracellular homeostasis by their Cu-chelating ability. In Arabidopsis (Arabidopsis thaliana), two Cu chaperones, Antioxidant Protein1 (ATX1) and ATX1-Like Copper Chaperone (CCH), share high sequence homology. Previously, their Cu-binding capabilities were demonstrated and interacting molecules were identified. To understand the physiological functions of these two chaperones, we characterized the phenotype of atx1 and cch mutants and the cchatx1 double mutant in Arabidopsis. The shoot and root growth of atx1 and cchatx1 but not cch was specifically hypersensitive to excess Cu but not excess iron, zinc, or cadmium. The activities of antioxidant enzymes in atx1 and cchatx1 were markedly regulated in response to excess Cu, which confirms the phenotype of Cu hypersensitivity. Interestingly, atx1 and cchatx1 were sensitive to Cu deficiency. Overexpression of ATX1 not only enhanced Cu tolerance and accumulation in excess Cu conditions but also tolerance to Cu deficiency. In addition, the Cu-binding motif MXCXXC of ATX1 was required for these physiological functions. ATX1 was previously proposed to be involved in Cu homeostasis by its Cu-binding activity and interaction with the Cu transporter Heavy metal-transporting P-type ATPase5. In this study, we demonstrate that ATX1 plays an essential role in Cu homeostasis in conferring tolerance to excess Cu and Cu deficiency. The possible mechanism is discussed.     

Effects of essential fatty acids on the reproduction of a generalist herbivore

We studied direct and indirect effects of essential fatty acids(EFA) on Daphnia magna reproduction. Daphnia females that receivedEFA enriched algae over their entire lifespan produced largerbroods than females fed control algae. However, EFA-enrichedfemales were also 91% heavier than control females, which potentiallyexplain the larger investment in reproduction. Thus, with sucha large difference in female mass, it is difficult to differentiatethe direct effect of the EFA addition from the indirect (maternalsize) effects on reproduction. To assess the direct effectson reproduction, we performed two experiments in which we enrichedfemale diets with a range of fatty acids. To minimize maternalsize differences, we applied the EFA enrichments only to maturedaphniids and studied the effects on reproduction during andafter two time intervals (15–16 and 7 days). Limitingthe enrichment phase until after maturity decreased the maternalsize differences over the enrichment phase among the fatty acidtreatments from an average of 91% (for life time enrichment)to 29% after 15–16 days maternal enrichment interval,to 18% after the 7 day interval. Minimizing size differencesbetween differently enriched females decreased the differencesin brood size and offspring size. Neonates from control femaleswere more severely affected by starvation than offspring fromfemales that received saturated and polyunsaturated fatty acidenrichments. Under low food concentrations, only neonates thathad access to polyunsaturated fatty acids had positive growthrates, thus showing that although dietary fatty acids can beused for energy purposes, specific fatty acids are requiredto build new biomass. One consequence of our findings is thatoffspring size does not serve as a good estimate of offspringquality when feeding on different resource qualities.     

Potassium flux in the pollen tubes was essential in plant sexual reproduction

Potassium channels are controlling K⁺ transport across plasma membrane and thus playing a central role in all aspects of osmolarity as well as numerous other functions in plants, including in sexual reproduction. We have used whole-cell and single-channel patch-clamp recording techniques investigated the regulation of intracellular free Ca²⁺-activated outward K⁺ channels in Pyrus pyrifolia pollen tube protoplasts. We have also showed the channels could be inhibited by heme and activated carbon monoxide (CO). In the presence of oxygen and NADPH, hemoxygenases catalyzes heme degradation, producing biliverdin, iron and CO. Considered the oxygen concentration approaching zero in the ovary, the heme will inhibit the K⁺ outward flux from the intracellular of pollen tube, increasing the pollen tubes osmolarity, inducing pollen tube burst. Here we discuss the putative role of K⁺ channels in plant sexual reproduction.Key words: pear, pollen, K⁺ channels, heme, carbon monoxideIon channels in the pollen tube play critical roles in mediation pollen germination and pollen tube growth.^1–3 Early studies were focus on the plasma membrane calcium channel regulation and cytosolic free calcium concentration variation in the pollen tube reason by which was one of the most important second messengers in plants.^3–7 However, reports have also showed that the potassium channels in the pollen tubes were also involved in several important steps of plant sexual reproduction.^8–19 Recently, more reports further demonstrated this phenomena.^20–24 In the report by Lu et al. they demonstrated that two cation/proton exchangers (CHX), CHX21 and CHX23, are essential for pollen tube growth guidance in Arabidopsis.²² chx21 chx23 double mutant induces the fertility impaired, but which is unchanged in both single chx21 or chx23 mutants. They have also found that the double mutant pollen grains germination and pollen tube growth in the transmitting tract were not difference with the wild-type, however, the double mutant pollen tubes fail to turn toward ovules.²² Protein localization experiments show CHX23 is expressed in the endoplasmic reticulum of pollen tubes; functional analysis results showed that CHX23 as a K⁺ transporter mediates K⁺ uptake in a pH-dependent manner. So, these protein affect the signal transduction pathway of pollen tube growth toward to the ovule by controlling the cation balance and pH in the pollen tube.²² Amien et al. identified a signaling ligand of defensin-like (DEFL) protein, ZmES4, which expressed in maize synergid. ZmES4 activates the maize pollen tube tip plasma membrane K⁺ Shaker channel KZM1.²⁰ This finding is also very interesting. Pollen tube bursting suggested to be based on the osmotic stress; the influx of K⁺ mediated by ZmES4-activated KZM1 will trigger rapid plasma membrane depolarization, which induced the pollen tube tip burst.²⁰ Furthermore, the osmotic increasing induced by too much K⁺ in the cytosolic of pollen tube was not only resulted by inward K⁺ channel activation, but also resulted by outward K⁺ channel inhibition in the pollen tube plasma membrane. In our report, we find a intracellular Ca²⁺-sensitive outward K⁺ channel in pear pollen tube plasma membrane, which could be inhibited by heme and activated by heme oxidative production, carbon monoxide (CO), may play a functional role in the pollen tube brusting.²³In the presence of oxygen and NADPH, hemoxygenases catalyzes heme degradation, producing biliverdin, iron and CO.²⁵ Early reports showed that oxygen plays an important role in plant sexual reproduction. Pollen tubes grow through the style toward the ovary with high speed, a process that consumes tremendous amounts of energy and requires rapid oxygen uptake by pollen tubes.²⁶ Pollen grains have roughly 20 times the level of mitochondria and respire 10 times faster than vegetative tissue.^12,27–29 Furthermore, oxygen has been proposed as a possible cue for pollen-tube guidance.³⁰ Indeed, the existence of an oxygen gradient in the unpollinated style has been shown in some species such as Hipeastrum hybridum. Oxygen pressure is high in the stigma and style but suddenly decreases at the base of the style, approaching zero in the ovary. Moreover, pollen-tube growth itself creates hypoxic regions within the style.³¹ Therefore, we suggest that the outward K⁺ channel inhibited by heme is dominant compared with which activated by CO when pollen tubes reach the ovary, based on where the hypoxic condition (Fig. 1). However, the gene encode the outward K⁺ channel in the pear pollen tube remains to be determined in the further study.Open in a separate windowFigure 1Reciprocal regulation of heme and carbon monoxide in putative Ca²⁺-activated outward K⁺ channel. Under normal condition, in the presence of NADPH, heme is metabolized by hemeoxygenase to generate carbon monoxide (CO), which activates outward K⁺ channel. However, without the oxygen, heme cannot be metabolized. The accumulated heme acts as an inhibitor of outward K⁺ channel, even in the presence of NADPH. The accumulated K⁺ in the cytosolic of pollen will induced the pollen tube depolarized, then burst.     

Copper supply and the leaf emergence rate of spring wheat

Copper deficiency can delay flowering and plant maturity. However, the effect of copper deficiency on the rate of leaf emergence has not been quantified. We tested the hypothesis that low copper supply decreases the rate of leaf emergence of wheat (Triticum aestivum L. cv Gamenya). Copper foliar sprays are commonly applied to wheat. We examined the response of the rate of leaf emergence to a foliar application of copper sulphate.Wheat was grown in root cooling tanks (20°C) in the glasshouse. Soil copper treatments were applied as solutions of CuSO₄.5H₂O at three rates: Cu₀=no added Cu, Cu₄₀₀=400 g Cu per 3 kg pot, and Cu₁₆₀₀=1600 g Cu per pot. An additional treatment of a foliar spray of CuSO₄.5H₂O (0.4 mg Cu per plant) was applied to Cu₀ and Cu₄₀₀ plants 45 days after sowing (5.5 leaves on the main stem). Leaves on the main stem were counted and the rate of leaf emergence was estimated from the regression of number of emerged leaves against thermal time (base 0°C). The phyllochron was calculated as 1/rate of emergence.Leaves on Cu₀ and Cu₄₀₀ plants took longer to emerge than on Cu₁₆₀₀ plants, with the phyllochron of Cu₁₆₀₀ plants being 130 compared to 137 for the Cu₄₀₀ plants and 158 for the Cu₀ plants. The foliar application of CuSO₄ at the 5–6 leaf stage resulted in a decrease in the phyllochron of the Cu₀ plants to 127, but no change in that of the Cu₄₀₀ plants.     

Biotransformation of constituents of essential oils by germinating wheat seed

Wheat seeds, when exposed to essential oils, are able to metabolise certain monoterpenes. The actual amounts of the compounds and their derivatives in the endosperm and embryo of wheat seeds, after exposure to the monoterpenes were determined. Neral and geranial, which are the constituents of citral, are reduced and oxidised to the corresponding alcohols and acids. Similarly citronellal, pulegone and carvacrol are converted partly to the corresponding reduction and oxidation products. The aromatic compound vanillin is partly reduced to vanillyl alcohol or oxidised to vanillic acid. In all cases it seems that part of the compounds applied are degraded, as indicated by the inability to account for all the compounds, which were supplied to the germinated seeds. In most cases the derivatives of the essential oil applied were less toxic than the parent compound. The possible role of non-specific enzymes by which the compounds are oxidised or reduced is discussed.