Growth and survival of cork oak (Quercus suber) seedlings after simulated partial cotyledon consumption under different soil nutrient contents

Aims

We examined the importance of partial seed consumption (cotyledon loss) by rabbits in the early establishment of seedlings of cork oaks restricted to nutrient-impoverished soils.

Methods

To determine the importance of cotyledons in the growth and development of seedlings, we simulated two levels of predation [light (30 % cotyledon loss) and heavy (60 % loss) partial consumption] and two soil nutrient contents (nutrient-poor soil, nutrient-rich soil). Seedlings height, root length, dry root and shoot biomass, specific leaf mass, leaf density, gas exchange, chlorophyll fluorescence parameters and photosynthetic pigment concentrations were determined.

Results

Results indicated that effect of nutrient level on the growth of the oak seedlings was more important than that of cotyledon biomass. However, in nutrient–poor soils, cotyledon biomass played a major role in the early performance of cork oaks. Acorns grown in nutrient-rich substrate, despite having greater aerial vigor, were slower to develop a vertical root, and hence less likely to reach permanent moisture. Cotyledon loss caused a decrease in the biomass of roots and shoots when acorns were heavily consumed, and as a result experienced a reduction in net photosynthetic rate, stomatal conductance and chlorophyll concentration. Survival of seedlings was unaffected by either soil type or cotyledon loss.

Conclusions

Our results show that effects of soil type on the survival of oak seedlings were more important than those of cotyledon biomass. However, in a competitive situation, cotyledon biomass, as an indicative of growth nutrient support rather than an energy source, could be vital in a nutrient-poor environment, particularly in Mediterranean climate regions and for species with little inherent drought tolerance (as is the case of Quercus spp.), where rapid root growth is required to ensure that contact with soil moisture is maintained over the first summer.     

Genetic Analysis of the Biosynthesis of 2-Methoxy-3-Isobutylpyrazine,a Major Grape-Derived Aroma Compound Impacting Wine Quality

Methoxypyrazines (MPs) are strongly odorant volatile molecules with vegetable-like fragrances that are widespread in plants. Some grapevine (Vitis vinifera) varieties accumulate significant amounts of MPs, including 2-methoxy-3-isobutylpyrazine (IBMP), which is the major MP in grape berries. MPs are of particular importance in white Sauvignon Blanc wines. The typicality of these wines relies on a fine balance between the pea pod, capsicum character of MPs and the passion fruit/grapefruit character due to volatile thiols. Although MPs play a crucial role in Sauvignon varietal aromas, excessive concentrations of these powerful odorants alter wine quality and reduce consumer acceptance, particularly in red wines. The last step of IBMP biosynthesis has been proposed to involve the methoxylation of the nonvolatile precursor 2-hydroxy-3-isobutylpyrazine to give rise to the highly volatile IBMP. In this work, we have used a quantitative trait loci approach to investigate the genetic bases of IBMP biosynthesis. This has led to the identification of two previously uncharacterized S-adenosyl-methionine-dependent O-methyltransferase genes, termed VvOMT3 and VvOMT4. Functional characterization of these two O-methyltransferases showed that the VvOMT3 protein was highly specific and efficient for 2-hydroxy-3-isobutylpyrazine methylation. Based on its differential expression in high- and low-MP-producing grapevine varieties, we propose that VvOMT3 is a key gene for IBMP biosynthesis in grapevine.The pleasure experienced while enjoying a glass of wine is the result of sophisticated sensory, neurophysiological, and psychological processes triggered by wine aroma. Wine flavor is the result of a complex mixture of volatile compounds in the headspace of the glass that induces feelings of pleasure at the brain level (Shepherd, 2006). During the last 40 years, over 800 volatile molecules have been formally identified in wines, in concentrations ranging from hundreds of milligrams per liter down to a few picograms per liter (Ebeler and Thorngate, 2009; Styger et al., 2011). Among all of them, a relatively limited number of compounds, called varietal (or primary) aromas, play a crucial role in wine flavor and typicality. These aromas, which are related to the grape variety, belong to a limited number of chemical families, including monoterpenes, C13 norisoprenoids, volatile sulfur compounds, and methoxypyrazines (MPs; Ebeler and Thorngate, 2009). Quite frequently, they exist mostly in the grape (Vitis vinifera) berry as nonvolatile, odorless, “bound” forms that can be released by chemical and enzymatic reactions occurring during the winemaking and wine aging processes, thus enhancing wine’s varietal expression (Styger et al., 2011). Two classical examples are the glycoside precursors of the monoterpenols (Strauss et al., 1986) and the cysteinylated or glutathionylated precursors of the volatile thiols (Tominaga et al., 1998; Peña-Gallego et al., 2012). Noticeable exceptions are the MPs, which are found in grape berries exclusively as free, volatile molecules.MPs are strongly odorant volatile heterocycles, with vegetable-like fragrances, that are widely occurring in the plant kingdom (Maga, 1982). In grape, they can be detected in fruits, leaves, shoots, and roots (Dunlevy et al., 2010). They are found in different grape varieties and are particularly abundant in the so-called Bordeaux cultivars (i.e. cv Cabernet Franc, Cabernet Sauvignon [CS], Sauvignon Blanc, Merlot, and Carménère [Car]; Bayonove et al., 1975; Lacey et al., 1991; Roujou de Boubée et al., 2002; Belancic and Agosin, 2007), whereas they are rarely detected in other cultivars, such as cv Pinot Noir (PN), Chardonnay, or Petit Verdot (PV). This finding indicates a strong genotype dependency of MP biosynthesis (Koch et al., 2010). MPs are accumulated in berries until bunch closure or véraison, and then their level declines after véraison (Hashizume and Samuta, 1999; Ryona et al., 2008). MP concentration in wine is highly correlated with the grape berry content at harvest (Roujou de Boubée et al., 2002). Three MPs are found in grape berries: 2-methoxy-3-isobutylpyrazine (IBMP), which is the most abundant, and two others, 2-methoxy-3-isopropylpyrazine (IPMP) and 2-methoxy-3-sec-butylpyrazine (SBMP; Ebeler and Thorngate, 2009). Both IBMP and IPMP display very low sensory detection thresholds in the wine matrix, ranging from 1 to 16 ng L^–1.MPs are of particular importance in white Sauvignon Blanc wines. The typicality of these wines relies on a fine balance between the pea pod, capsicum character of MPs and the passion fruit/grapefruit character due to volatile thiols (Dubourdieu et al., 2006; Lund et al., 2009). Although MPs play a crucial role in Sauvignon varietal aromas, excessive concentrations of these extremely powerful odorants will reduce consumer acceptance (Parr et al., 2007). In red wine, MPs are considered as off-flavor, and red wines can be depreciated by concentrations above 10 ng L^–1 (Allen et al., 1991; Roujou de Boubée et al., 2000; Belancic and Agosin, 2007). Given the importance of MPs, either as typical varietal aromas or as detrimental off-flavors, deciphering the genetic and molecular determinism of their accumulation is of high interest for viticulture.In spite of this, until recently little was known about the MP biosynthesis pathway or the MP biosynthetic genes, either in grapevine or other plant species. Theoretical biosynthesis pathways have been proposed since the mid-1970s. They all start by the addition of an α-dicarbonyl on a branched amino acid (Leu for IBMP, Val for IPMP) to form a 2-hydroxy-3-alkylpyrazine, which is subsequently transformed into the corresponding MP, by a methoxylation reaction (Murray and Whitfield 1975; Gallois et al., 1988). While the initial addition step remains to be demonstrated in plants, an S-adenosyl-l-Met (SAM)-dependent O-methyltransferase (OMT), capable of converting 2-hydroxy-3-isobutylpyrazine (IBHP) into IBMP, has been detected in CS shoots, partially purified and sequenced (Hashizume et al., 2001a, 2001b; Fig. 1). Recently, Dunlevy et al. (2010) characterized two OMTs, VvOMT1 and VvOMT2, capable of methylating IBHP in vitro, albeit with high apparent K_m values. To investigate the genetic bases of MP biosynthesis in grape berries, we performed a quantitative trait loci (QTL) analysis, which has led to the identification of two previously uncharacterized OMTs termed VvOMT3 and VvOMT4. Functional characterization of these two OMTs showed that VvOMT3 was highly specific and efficient for IBHP methylation. Based on its differential expression in high-MP and low-MP grapevine varieties, we propose that VvOMT3 and, to a lesser extent, VvOMT4 are key genes for MP biosynthesis in grapevine berries.Open in a separate windowFigure 1.Putative biosynthesis pathway for IBMP adapted from Hashizume et al. (2001a). SAHcy, S-Adenosyl-l-homo-Cys.     

Status of arctic charr (Salvelinus alpinus) farming in Norway, Sweden and Iceland

This article describes the status of the Arctic charr (Salvelinus alpinus L.) aquaculture industry in Iceland, Norway and Sweden. The purpose of the work was to give an update on the status of Arctic charr farming in these countries based on information obtained from the industry itself. The data were collected using questionnaires designed for the purpose with key personnel in each country interviewing the farmers or farm managers. The questions were divided on topics focusing on different sides of the production, including farm characteristics, biological challenges and markets. The aim was to identify strengths and weaknesses in the production related to country and production technologies. The information may prove useful for decisions and prioritising future research and development work on removing bottlenecks and improving sustainable production of Arctic charr.     

Predation of Alouatta puruensis by Boa constrictor

Reports of successful predator attacks on primates are rare. Primates from all major radiations are particularly susceptible to raptors, carnivores, and snakes. Among New World primates, reports of snake predation are limited to medium- and small-bodied species. Here, we report the first documented case of successful predation of an atelid by a snake—an adult female Purús red howler monkey, Alouatta puruensis, that was subdued by a ca. 2-m-long Boa constrictor in an arboreal setting at a height of 7.5 m above the ground. The victim belonged to a group composed of six individuals (one adult male, two adult females, two juveniles, and one infant) that inhabited a ca. 2.5-ha forest fragment in the State of Rondônia, western Brazilian Amazon. The boa applied the species’ typical hunting behavior of striking and immediately coiling around its prey and then killing it through constriction (probably in less than 5 min), but the entire restraint period lasted 38 min. The attack occurred around noon. The howler was swallowed head-first in 76 min. The only group member to respond to the distress vocalization emitted by the victim was the other adult female, which was closest to the location where the attack occurred. This female ran toward the snake, also vocalizing, and hit it with her hands several times, but the snake did not react and she moved off to a nearby tree from where she watched most of the interaction. The remaining group members stayed resting at a height approximately 15 m above the victim in a nearby tree without showing any overt signs of stress, except for a single whimper vocalization. This event indicates that even large-bodied atelids are vulnerable to predation by large snakes and suggests that B. constrictor may be a more common predator of primates.     

The Highly Conserved Layer-3 Component of the HIV-1 gp120 Inner Domain Is Critical for CD4-Required Conformational Transitions

The trimeric envelope glycoprotein (Env) of human immunodeficiency virus type 1 (HIV-1) mediates virus entry into host cells. CD4 engagement with the gp120 exterior envelope glycoprotein subunit represents the first step during HIV-1 entry. CD4-induced conformational changes in the gp120 inner domain involve three potentially flexible topological layers (layers 1, 2, and 3). Structural rearrangements between layer 1 and layer 2 have been shown to facilitate the transition of the envelope glycoprotein trimer from the unliganded to the CD4-bound state and to stabilize gp120-CD4 interaction. However, our understanding of CD4-induced conformational changes in the gp120 inner domain remains incomplete. Here, we report that a highly conserved element of the gp120 inner domain, layer 3, plays a pivot-like role in these allosteric changes. In the unliganded state, layer 3 modulates the association of gp120 with the Env trimer, probably by influencing the relationship of the gp120 inner and outer domains. Importantly, layer 3 governs the efficiency of the initial gp120 interaction with CD4, a function that can also be fulfilled by filling the Phe43 cavity. This work defines the functional importance of layer 3 and completes a picture detailing the role of the gp120 inner domain in CD4-induced conformational transitions in the HIV-1 Env trimer.     

Nonhuman Transferrin Receptor 1 Is an Efficient Cell Entry Receptor for Ocozocoautla de Espinosa Virus

Ocozocoautla de Espinosa virus (OCEV) is a novel, uncultured arenavirus. We found that the OCEV glycoprotein mediates entry into grivet and bat cells through transferrin receptor 1 (TfR1) binding but that OCEV glycoprotein precursor (GPC)-pseudotyped retroviruses poorly entered 53 human cancer cell lines. Interestingly, OCEV and Tacaribe virus could use bat, but not human, TfR1. Replacing three human TfR1 amino acids with their bat ortholog counterparts transformed human TfR1 into an efficient OCEV and Tacaribe virus receptor.     

Tradeoffs in basal area growth and reproduction shift over the lifetime of a long-lived tropical species

Understanding of the extent to which reproductive costs drive growth largely derives from reproductively mature temperate trees in masting and non-masting years. We modeled basal area increment (BAI) and explored current growth–reproduction tradeoffs and changes in such allocation over the life span of a long-lived, non-masting tropical tree. We integrated rainfall and soil variables with data from 190 Bertholletia excelsa trees of different diameter at breast height (DBH) sizes, crown characteristics, and liana loads, quantifying BAI and reproductive output over 4 and 6 years, respectively. While rainfall explains BAI in all models, regardless of DBH class or ontogenic stage, light (based on canopy position and crown form) is most critical in the juvenile (5 cm ≤ DBH < 50 cm) phase. Suppressed trees are only present as juveniles and grow ten times slower (1.45 ± 2.73 m² year^?1) than trees in dominant and co-dominant positions (13.25 ± 0.82 and 12.90 ± 1.35 m² year^?1, respectively). Additionally, few juvenile trees are reproductive, and those that are, demonstrate reduced growth, as do reproductive trees in the next 50 to 100 cm DBH class, suggesting growth–reproduction tradeoffs. Upon reaching the canopy, however, and attaining a sizeable girth, this pattern gradually shifts to one where BAI and reproduction are influenced independently by variables such as liana load, crown size and soil properties. At this stage, BAI is largely unaffected by fruit production levels. Thus, while growth–reproduction tradeoffs clearly exist during early life stages, effects of reproductive allocation diminish as B. excelsa increases in size and maturity.     

Diversity and diversification of Eumolpinae (Coleoptera: Chrysomelidae) in New Caledonia

Contemporary taxonomic work on New Caledonian Eumolpinae (Chrysomelidae) has revealed their high species richness in this Western Pacific biodiversity hotspot. To estimate total species richness in this community, we used rapid DNA‐based biodiversity assessment tools, exploring mtDNA diversity and phylogenetic structure in a sample of 840 specimens across the main island. Concordance of morphospecies delimitation with units delimited by phenetic and phylogenetic algorithms revealed some 98–110 species in our sample, twice as many as currently described. Sample‐based rarefaction curves and species estimators using these species counts doubled this figure (up to 210 species), a realistic estimate considering taxonomic coverage, local endemism, and characteristics of sampling design, amongst others. New Caledonia, compared with larger tropical islands, stands out as a hotspot for Eumolpinae biodiversity. Molecular dating using either chrysomelid specific rates or tree calibration using palaeogeographical data dated the root of the ingroup tree (not necessarily a monophyletic radiation) at 38.5 Mya, implying colonizations after the Cretaceous breakage of Gondwana. Our data are compatible with the slowdown in diversification rates through time and are also consistent with recent faunal origins, possibly reflecting niche occupancy after an initial rapid diversification. Environmental factors (e.g. soil characteristics) seemingly played a role in this diversification process. © 2013 The Linnean Society of London     

Geographical patterns of genetic variation in rosemary (Rosmarinus officinalis) in the Mediterranean basin

Climate changes during the Quaternary had important effects on the evolution of European plant species. The distribution of genetic variability in rosemary, a strictly Mediterranean species of reputed Plio‐Quaternary origin for which the diversification centre is hypothesized to be located in the western part of the Mediterranean basin, was investigated across the species range by using plastid microsatellites [plastid simple sequence repeat (cpSSR)] markers. Seven out of the 17 primer pairs screened were polymorphic, with up to four alleles, yielding a total of 17 size variants combined into ten haplotypes. A permutation test to investigate for geographical structure showed no significant differences between R_ST and G_ST, indicating that the species lacks geographical structure. Low correlation between genetic and geographical distances was shown by the Mantel test. Bayesian analysis identified two coancestry groups of populations. The distribution of genetic diversity supports the hypothesized origin in the western Mediterranean basin, and with the demographic expansion test indicates three different routes of migration: a northern route expanding along the northern side of the Mediterranean and two southern routes, one from west to east through North Africa and reaching Cyrenaica, and a second to the south‐west of the Iberian Peninsula, from where it came back to the south–central areas. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013 , 171 , 700–712.