Male allocation to ejaculation and mating effort imposes different life history trade-offs.

When males compete, sexual selection favors reproductive traits that increase their mating or fertilization success (pre- and postcopulatory sexual selection). It is assumed that males face a trade-off between these 2 types of sexual traits because they both draw from the same pool of resources. Consequently, allocation into mate acquisition or ejaculation should create similar trade-offs with other key life history traits. Tests of these assumptions are exceedingly rare. Males only ejaculate after they mate, and the costs of ejaculation are therefore highly confounded with those of mating effort. Consequently, little is known about how each component of reproductive allocation affects a male's future performance. Here, we ran an experiment using a novel technique to distinguish the life history costs of mating effort and ejaculation for mosquitofish (Gambusia holbrooki). We compared manipulated males (mate without ejaculation), control males (mate and ejaculate), and naïve males (neither mate nor ejaculate) continuously housed with a female and 2 rival males. We assessed their growth, somatic maintenance, mating and fighting behavior, and sperm traits after 8 and 16 weeks. Past mating effort significantly lowered a male's future mating effort and growth, but not his sperm production, while past sperm release significantly lowered a male's future ejaculate quantity, but not his mating effort. Immune response was the only trait impacted by both past mating effort and past ejaculation. These findings challenge the assumption that male reproductive allocation draws from a common pool of resources to generate similar life history costs later in life. Instead, we provide clear evidence that allocation into traits under pre- and postcopulatory sexual selection have different trait-specific effects on subsequent male reproductive performance.

Genetic mapping of loci affecting seedling and adult-plant resistance to powdery mildew derived from two CIMMYT wheat lines.

MAIN CONCLUSION: PM3 and PM8 alleles carried by two CIMMYT wheat lines confer powdery mildew resistance in seedlings and/or adult plants. A stage-specific epistatic interaction was observed between PM3 and PM8. Powdery mildew is an important foliar disease of wheat. Major genes for resistance, which have been widely used in wheat breeding programs, are typically effective against only limited numbers of virulence genes of the pathogen. The main aim of this study was to map resistance loci in wheat lines 7HRWSN58 and ZWW09-149 from the International Maize and Wheat Improvement Center (CIMMYT). Doubled haploid populations (Magenta/7HRWSN58 and Emu Rock/ZWW09-149) were developed and grown in controlled environment experiments and inoculated with a composite of Blumeria graminis f.sp. tritici isolates that had been collected at various locations in Western Australia. Plants were assessed for powdery mildew symptoms (percentage leaf area diseased) on seedlings and adult plants. Populations were subjected to genotyping-by-sequencing and assayed for known SNPs in the resistance gene PM3. Linkage maps were constructed, and markers were anchored to the wheat reference genome sequence. In both populations, there were asymptomatic lines that exhibited no symptoms. Among symptomatic lines, disease severity varied widely. In the Magenta/7HRWSN58 population, most of the observed variation was attributed to the PM3 region of chromosome 1A, with the allele from 7HRWSN58 conferring resistance in seedlings and adult plants. In the Emu Rock/ZWW09-149 population, two interacting quantitative trait loci were mapped: one at PM3 and the other on chromosome 1B. The Emu Rock/ZWW09-149 population was confirmed to segregate for a 1BL·1RS translocation that carries the PM8 powdery mildew resistance gene from rye. Consistent with previous reports that PM8-derived resistance can be suppressed by PM3 alleles, the observed interaction between the quantitative trait loci on chromosomes 1A and 1B indicated that the PM3 allele carried by ZWW09-149 suppresses PM8-derived resistance from ZWW09-149, but only at the seedling stage. In adult plants, the PM8 region conferred resistance regardless of the PM3 genotype. The resistance sources and molecular markers that were investigated here could be useful in wheat breeding.

An international wheat diversity panel reveals novel sources of genetic resistance to tan spot in Australia.

KEY MESSAGE: Novel sources of genetic resistance to tan spot in Australia have been discovered using one-step GWAS and genomic prediction models that accounts for additive and non-additive genetic variation. Tan spot is a foliar disease in wheat caused by the fungal pathogen Pyrenophora tritici-repentis (Ptr) and has been reported to generate up to 50% yield losses under favourable disease conditions. Although farming management practices are available to reduce disease, the most economically sustainable approach is establishing genetic resistance through plant breeding. To further understand the genetic basis for disease resistance, we conducted a phenotypic and genetic analysis study using an international diversity panel of 192 wheat lines from the Maize and Wheat Improvement Centre (CIMMYT), the International Centre for Agriculture in the Dry Areas (ICARDA) and Australian (AUS) wheat research programmes. The panel was evaluated using Australian Ptr isolates in 12 experiments conducted in three Australian locations over two years, with assessment for tan spot symptoms at various plant development stages. Phenotypic modelling indicated high heritability for nearly all tan spot traits with ICARDA lines displaying the greatest average resistance. We then conducted a one-step whole-genome analysis of each trait using a high-density SNP array, revealing a large number of highly significant QTL exhibiting a distinct lack of repeatability across the traits. To better summarise the genetic resistance of the lines, a one-step genomic prediction of each tan spot trait was conducted by combining the additive and non-additive predicted genetic effects of the lines. This revealed multiple CIMMYT lines with broad genetic resistance across the developmental stages of the plant which can be utilised in Australian wheat breeding programmes to improve tan spot disease resistance.

CrebA increases secretory capacity through direct transcriptional regulation of the secretory machinery, a subset of secretory cargo, and other key regulators.

Specialization of many cells, including the acinar cells of the salivary glands and pancreas, milk-producing cells of mammary glands, mucus-secreting goblet cells, antibody-producing plasma cells, and cells that generate the dense extracellular matrices of bone and cartilage, requires scaling up both secretory machinery and cell-type specific secretory cargo. Using tissue-specific genome-scale analyses, we determine how increases in secretory capacity are coordinated with increases in secretory load in the Drosophila salivary gland (SG), an ideal model for gaining mechanistic insight into the functional specialization of secretory organs. Our findings show that CrebA, a bZIP transcription factor, directly binds genes encoding the core secretory machinery, including protein components of the signal recognition particle and receptor, ER cargo translocators, Cop I and Cop II vesicles, as well as the structural proteins and enzymes of these organelles. CrebA directly binds a subset of SG cargo genes and CrebA binds and boosts expression of Sage, a SG-specific transcription factor essential for cargo expression. To further enhance secretory output, CrebA binds and activates Xbp1 and Tudor-SN. Thus, CrebA directly upregulates the machinery of secretion and additional factors to increase overall secretory capacity in professional secretory cells; concomitant increases in cargo are achieved both directly and indirectly.

Sarcopenia in liver cirrhosis: Prevalence, pathophysiology and therapeutic strategies.

Sarcopenia, characterized by a loss of muscle strength, quantity/quality, and physical performance is associated with increased mortality and poor clinical outcomes in concomitant presentation with liver cirrhosis (LC). A number of mechanisms are involved in sarcopenia development in LC, many of which are secondary to liver dysfunction and/or iatrogenic involvement in treating LC. Sarcopenia severity in this population appears to be affected by patient gender, as well as the primary aetiology of LC (alcohol, non-alcoholic fatty liver disease etc.) with patient demographics shifting in recent years. Clinical detection of sarcopenia in this population may involve a combination of assessment tools, in addition to measuring muscle mass and strength separately. Muscle mass may be assessed using radiography, bioelectric impedance, ultrasound, or anthropometrics. Hand-grip strength, on the other hand, may be a useful tool for evaluating muscle strength. The role of malnutrition in sarcopenia is also a relevant factor, and screening tools such as MELD and SARC-F may be clinically useful tools for more complete diagnosis of sarcopenia in these patients. Myostatin and titin-N may represent potential diagnostic biomarkers. Lastly, physical activity and nutrition remain key elements of treatment. Further research is being conducted regarding the role of resistance vs aerobic exercise as well as the function of complementary nutrition. Continued study into the role of nutrition, physical activity and other complementary therapies will be important future endeavours in the treatment of sarcopenia in LC.

Male age alone predicts paternity success under sperm competition when effects of age and past mating effort are experimentally separated.

Older males often perform poorly under post-copulatory sexual selection. It is unclear, however, whether reproductive senescence is because of male age itself or the accumulated costs of the higher lifetime mating effort that is usually associated with male age. To date, very few studies have accounted for mating history and sperm storage when testing the effect of male age on sperm traits, and none test how age and past mating history influence paternity success under sperm competition. Here, we experimentally manipulate male mating history to tease apart its effects from that of age on ejaculate traits and paternity in the mosquitofish, Gambusia holbrooki. We found that old, naive males had more sperm than old, experienced males, while the reverse was true for young males. By contrast, neither male age nor mating history affected sperm velocity. Finally, using artificial insemination to experimentally control the number of sperm per male, we found that old males sired significantly more offspring than young males independently of their mating history. Our results highlight that the general pattern of male reproductive senescence described in many taxa may often be affected by two naturally confounding factors, male mating history and sperm age, rather than male age itself.

Dormancy and dormancy release in white-grained wheat (Triticum aestivum L.).

MAIN CONCLUSION: Dormancy in white-grained wheat is conditioned by the cumulative effects of several QTL that delay the onset of the capacity to germinate during ripening and after-ripening. Grain dormancy at harvest-ripeness is a major component of resistance to preharvest sprouting in wheat (Triticum aestivum L.) and an important trait in regions where rain is common during the harvest period. Breeding lines developed in Australia maintained their dormancy phenotype over multiple seasons and during grain ripening, the time between anthesis and the acquisition of the capacity to germinate, dormancy release, increased in line with the strength of dormancy. Genetic dissection of two dormant lines indicated that dormancy was due to the cumulative action of between one and three major genetic loci and several minor loci. This presents a significant challenge for breeders targeting environments with a high risk of sprouting where strong dormancy is desirable. Only around half of the difference in dormancy between the dormant lines and a non-dormant variety could be attributed to the major genetic loci on chromosomes 4A and 3A. A QTL that was mapped on chromosome 5A may be an orthologue of a minor QTL for dormancy in barley. At each locus, the dormancy allele increased the time to dormancy release during ripening. In combination, these alleles had cumulative effects. Embryo sensitivity to abscisic acid was related to the dormancy phenotype of the whole caryopsis, however, changes in concentrations of abscisic acid and gibberellins in embryo sections and de-embryonated grains during ripening and after-ripening could not be linked to the timing of dormancy release.

Repeatability of lateralisation in mosquitofish Gambusia holbrooki despite evidence for turn alternation in detour tests.

Akin to handedness in humans, some animals show a preference for moving to the left or right. This is often attributed to lateralised cognitive functions and eye dominance, which, in turn, influences their behaviour. In fishes, behavioural lateralisation has been tested using detour mazes for over 20 years. Studies report that certain individuals are more likely to approach predators or potential mates from one direction. These findings imply that the lateralisation behaviour of individuals is repeatable, but this is rarely confirmed through multiple testing of each individual over time. Here we quantify the repeatability of turning behaviour by female mosquitofish (Gambusia holbrooki) in a double sided T-maze. Each female was tested three times in each of six treatments: when approaching other females, males, or an empty space; and when able to swim freely or when forced to choose by being herded from behind with a net. Although there was no turning bias based on the mean population response, we detected significant repeatability of lateralisation in five of the six treatments (R = 0.251-0.625). This is noteworthy as we also found that individuals tended to alternate between left and right turns, meaning that they tend to move back and forth along one wall of the double-sided T-maze. Furthermore, we found evidence for this wall following when re-analysing data from a previous study. We discuss potential explanations for this phenomenon, and its implications for study design.

Differential effects of low-dose sacubitril and/or valsartan on renal disease in salt-sensitive hypertension.

Diuretics and renin-angiotensin system blockers are often insufficient to control the blood pressure (BP) in salt-sensitive (SS) subjects. Abundant data support the proposal that the level of atrial natriuretic peptide may correlate with the pathogenesis of SS hypertension. We hypothesized here that increasing atrial natriuretic peptide levels with sacubitril, combined with renin-angiotensin system blockage by valsartan, can be beneficial for alleviation of renal damage in a model of SS hypertension, the Dahl SS rat. To induce a BP increase, rats were challenged with a high-salt 4% NaCl diet for 21 days, and chronic administration of vehicle or low-dose sacubitril and/or valsartan (75 µg/day each) was performed. Urine flow, Na+ excretion, and water consumption were increased on the high-salt diet compared with the starting point (0.4% NaCl) in all groups but remained similar among the groups at the end of the protocol. Upon salt challenge, we observed a mild decrease in systolic BP and urinary neutrophil gelatinase-associated lipocalin levels (indicative of alleviated tubular damage) in the valsartan-treated groups. Sacubitril, as well as sacubitril/valsartan, attenuated the glomerular filtration rate decline induced by salt. Alleviation of protein cast formation and lower renal medullary fibrosis were observed in the sacubitril/valsartan- and valsartan-treated groups, but not when sacubitril alone was administered. Interestingly, proteinuria was mildly mitigated only in rats that received sacubitril/valsartan. Further studies of the effects of sacubitril/valsartan in the setting of SS hypertension, perhaps involving a higher dose of the drug, are warranted to determine if it can interfere with the progression of the disease.

Fine-scale genital morphology affects male ejaculation success: an experimental test.

The evolution of male genital traits is usually ascribed to advantages that arise when there is sperm competition, cryptic female choice or sexual conflict. However, when male-female contact is brief and sperm production is costly, genital structures that ensure the appropriate timing of sperm release should also be under intense selection. Few studies have examined the role of individual structures in triggering ejaculation. We therefore conducted a series of anatomical manipulations of fine-scale features of the complex intromittent organ (gonopodium) of a freshwater fish with internal fertilization (Gambusia holbrooki) to determine their effects on sperm release. Mating in G. holbrooki is fleeting (less than 50 ms), so there should be strong selection for control over the timing of sperm release. We surgically removed three features at the tip of the gonopodium (claws, spines, awl-shape) to test for their potential role in triggering ejaculation. We show that the 'awl-shape' of the tip affects sperm release when a male makes contact with a female, but neither gonopodial claws nor spines had a detectable effect. We suggest that the claws and spines may instead function to increase the precision of sperm deposition (facilitating anchorage and contact time with the female's gonopore), rather than the initiation of ejaculation.

An experimental test of the role of male mating history on paternal effects in the livebearer fish Gambusia holbrooki.

Studies often show that paternal age affects offspring fitness. However, such effects could be due either to age, or to a male's previous mating effort (which is necessarily confounded with age). We experimentally tested whether differences in the mating history of old males affect offspring performance in the mosquitofish Gambusia holbrooki. Upon maturation, males were housed for a duration of the natural field-breeding season (23 weeks) either with mating access to females (lifetime-mating), or with visual but no physical access to females (no-mating). We then paired these males with a female to test whether male mating history had a significant effect on their mate's breeding success or offspring performance. The daughters, but not the sons, of 'no-mating' treatment males matured significantly sooner, and at a significantly smaller size, than those of 'lifetime-mating' treatment males. There was, however, no effect of male mating history on their daughters' initial fecundity, or on proxy measures of their sons' reproductive success. These results, when combined with earlier studies showing effects of male mating history on sperm quality, growth and immunity, suggest that variation in paternal effects currently attributed to male age could partly arise because older males have usually mated more often than younger males.

Molecular screening of familial hypercholesterolemia in Icelanders.

Familial hypercholesterolemia (FH) is a monogenic disease characterized by a lifelong exposure to high LDL-C levels that can lead to early onset coronary heart disease (CHD). The main causes of FH identified to date include loss-of-function mutations in LDLR or APOB, or gain-of-function mutations in PCSK9. Early diagnosis and genetic testing of FH suspects is critical for improved prognosis of affected individuals as lipid lowering treatments are effective in preventing CHD related morbidity and mortality. In the present study, we carried out a comprehensive screening, using a next-generation sequencing (NGS) panel, for FH culprit mutations in two Icelandic studies representative of either FH families or the general population. We confirmed all previously known mutations in the FH families, and identified two subjects that had been misdiagnosed clinically at young age. We identified six new mutations in the Icelandic FH families and detected three pathogenic mutations in the general population-based study. The application of the NGS panel revealed substantial diagnostic yields in identifying pathogenic mutations, or 68.2% of those with definite clinical diagnosis of FH in the family material and 5.6-fold enrichment in the population-based genetic testing.

An experimental test for body size-dependent effects of male harassment and an elevated copulation rate on female lifetime fecundity and offspring performance.

Many studies investigate the benefits of polyandry, but repeated interactions with males can lower female reproductive success. Interacting with males might even decrease offspring performance if it reduces a female's ability to transfer maternal resources. Male presence can be detrimental for females in two ways: by forcing females to mate at a higher rate and through costs associated with resisting male mating attempts. Teasing apart the relative costs of elevated mating rates from those of greater male harassment is critical to understand the evolution of mating strategies. Furthermore, it is important to test whether a male's phenotype, notably body size, has differential effects on female reproductive success versus the performance of offspring, and whether this is due to male body size affecting the costs of harassment or the actual mating rate. In the eastern mosquitofish Gambusia holbrooki, males vary greatly in body size and continually attempt to inseminate females. We experimentally manipulated male presence (i.e., harassment), male body size and whether males could copulate. Exposure to males had strong detrimental effects on female reproductive output, growth and immune response, independent of male size or whether males could copulate. In contrast, there was a little evidence of a cross-generational effect of male harassment or mating rate on offspring performance. Our results suggest that females housed with males pay direct costs due to reduced condition and offspring production and that these costs are not a consequence of increased mating rates. Furthermore, exposure to males does not affect offspring reproductive traits.

Temperature influences habitat preference of coral reef fishes: Will generalists become more specialised in a warming ocean?

Climate change is expected to pose a significant risk to species that exhibit strong behavioural preferences for specific habitat types, with generalist species assumed to be less vulnerable. In this study, we conducted habitat choice experiments to determine how water temperature influences habitat preference for three common species of coral reef damselfish (Pomacentridae) that differ in their levels of habitat specialisation. The lemon damselfish Pomacentrus moluccensis, a habitat specialist, consistently selected complex coral habitat across all temperature treatments (selected based on local average seasonal temperatures naturally experienced in situ: ambient winter 22°C; ambient summer 28°C; and elevated 31°C). Unexpectedly, the neon damselfish Pomacentrus coelestis and scissortail sergeant Abudefduf sexfasciatus, both of which have more generalist habitat associations, developed strong habitat preferences (for complex coral and boulder habitat, respectively) at the elevated temperature treatment (31°C) compared to no single preferred habitat at 22°C or 28°C. The observed shifts in habitat preference with temperature suggest that we may be currently underestimating the vulnerability of some habitat generalists to climate change and highlight that the ongoing loss of complex live coral through coral bleaching could further exacerbate resource overlap and species competition in ways not currently considered in climate change models.

'Stick with your own kind, or hang with the locals?' Implications of shoaling strategy for tropical reef fish on a range-expansion frontline.

Range shifts of tropical marine species to temperate latitudes are predicted to increase as a consequence of climate change. To date, the research focus on climate-mediated range shifts has been predominately dealt with the physiological capacity of tropical species to cope with the thermal challenges imposed by temperate latitudes. Behavioural traits of individuals in the novel temperate environment have not previously been investigated, however, they are also likely to play a key role in determining the establishment success of individual species at the range-expansion forefront. The aim of this study was to investigate the effect of shoaling strategy on the performance of juvenile tropical reef fishes that recruit annually to temperate waters off the south east coast of Australia. Specifically, we compared body-size distributions and the seasonal decline in abundance through time of juvenile tropical fishes that shoaled with native temperate species ('mixed' shoals) to those that shoaled only with conspecifics (as would be the case in their tropical range). We found that shoaling with temperate native species benefitted juvenile tropical reef fishes, with individuals in 'mixed' shoals attaining larger body-sizes over the season than those in 'tropical-only' shoals. This benefit in terms of population body-size distributions was accompanied by greater social cohesion of 'mixed' shoals across the season. Our results highlight the impact that sociality and behavioural plasticity are likely to play in determining the impact on native fish communities of climate-induced range expansion of coral reef fishes.

Good parenting may not increase reproductive success under environmental extremes.

For species exhibiting parental care, the way in which parents adjust care behaviour to compensate for environmental change potentially influences offspring survival and, ultimately, population viability. Using the three-spined stickleback (Gasterosteus aculeatus) - a species in which males provide parental care by building and tending a nest and fanning the eggs - we examined how low dissolved oxygen (DO) levels affect paternal care, embryo development and survival. Although levels of nest tending were unaffected by DO level, we found that larger males fanned their embryos more under low oxygen conditions. This resulted in faster rates of embryo development within the clutches of these larger males, but reduced embryo survival at 7 days post-fertilization compared to clutches of smaller males. Our results suggest that although parents may attempt to compensate for environmental change via alterations to care behaviour, their ability to do so can be dependent on parental phenotype. This sets up the potential for oxygen levels to act on the strength and direction of selection within populations. We discuss possible explanations for the surprising result that supposedly adaptive changes in care behaviour by large males (i.e. increased fanning) led to reduced embryo survival at 7 days post-fertilization, and whether, as a consequence, acute environmental conditions may have the potential to overwhelm selection on sexual traits.

Measurement tools for assessment of older age bipolar disorder: A systematic review of the recent global literature.

OBJECTIVES: More than 50% of people with bipolar disorder will be age 60 years or older by 2030. There is a need for more data to guide assessment and treatment in older age bipolar disorder (OABD); however, interpretation of findings from small, single-site studies may not be generalizable and there are few large trials. As a step in the direction of coordinated large-scale OABD data collection, it is critical to identify which measurements are currently used and identify potential gaps in domains typically assessed. METHODS: An international group of OABD experts performed a systematic literature review to identify studies examining OABD in the past 6 years. Relevant articles were assessed to categorize the types of clinical, cognitive, biomarker, and neuroimaging OABD tools routinely used in OABD studies. RESULTS: A total of 53 papers were identified, with a broad range of assessments. Most studies evaluated demographic and clinical domains, with fewer studies assessing cognition. There are relatively few biomarker and neuroimaging data, and data collection methods were less comprehensively covered. CONCLUSION: Assessment tools used in the recent OABD literature may help to identify both a minimum and a comprehensive dataset that should be evaluated in OABD. Our review also highlights gaps where key clinical outcomes have not been routinely assessed. Biomarker and neuroimaging assessment could be further developed and standardized. Clinical data could be combined with neuroimaging, genetic, and other biomarkers in large-scale coordinated data collection to further improve our understanding of OABD phenomenology and biology, thereby contributing to research that advances care.

Comprehensive genetic testing for female and male infertility using next-generation sequencing.

PURPOSE: To develop a comprehensive genetic test for female and male infertility in support of medical decisions during assisted reproductive technology (ART) protocols. METHODS: We developed a next-generation sequencing (NGS) gene panel consisting of 87 genes including promoters, 5' and 3' untranslated regions, exons, and selected introns. In addition, sex chromosome aneuploidies and Y chromosome microdeletions were analyzed concomitantly using the same panel. RESULTS: The NGS panel was analytically validated by retrospective analysis of 118 genomic DNA samples with known variants in loci representative of female and male infertility. Our results showed analytical accuracy of > 99%, with > 98% sensitivity for single-nucleotide variants (SNVs) and > 91% sensitivity for insertions/deletions (indels). Clinical sensitivity was assessed with samples containing variants representative of male and female infertility, and it was 100% for SNVs/indels, CFTR IVS8-5T variants, sex chromosome aneuploidies, and copy number variants (CNVs) and > 93% for Y chromosome microdeletions. Cost analysis shows potential savings when comparing this single NGS assay with the standard approach, which includes multiple assays. CONCLUSIONS: A single, comprehensive, NGS panel can simplify the ordering process for healthcare providers, reduce turnaround time, and lower the overall cost of testing for genetic assessment of infertility in females and males, while maintaining accuracy.

Loci on chromosomes 1A and 2A affect resistance to tan (yellow) spot in wheat populations not segregating for tsn1.

KEY MESSAGE: QTL for tan spot resistance were mapped on wheat chromosomes 1A and 2A. Lines were developed with resistance alleles at these loci and at the tsn1 locus on chromosome 5B. These lines expressed significantly higher resistance than the parent with tsn1 only. Tan spot (syn. yellow spot and yellow leaf spot) caused by Pyrenophora tritici-repentis is an important foliar disease of wheat in Australia. Few resistance genes have been mapped in Australian germplasm and only one, known as tsn1 located on chromosome 5B, is known in Australian breeding programs. This gene confers insensitivity to the fungal effector ToxA. The main aim of this study was to map novel resistance loci in two populations: Calingiri/Wyalkatchem, which is fixed for the ToxA-insensitivity allele tsn1, and IGW2574/Annuello, which is fixed for the ToxA-sensitivity allele Tsn1. A second aim was to combine new loci with tsn1 to develop lines with improved resistance. Tan spot severity was evaluated at various growth stages and in multiple environments. Symptom severity traits exhibited quantitative variation. The most significant quantitative trait loci (QTL) were detected on chromosomes 2A and 1A. The QTL on 2A explained up to 29.2% of the genotypic variation in the Calingiri/Wyalkatchem population with the resistance allele contributed by Wyalkatchem. The QTL on 1A explained up to 28.1% of the genotypic variation in the IGW2574/Annuello population with the resistance allele contributed by Annuello. The resistance alleles at both QTL were successfully combined with tsn1 to develop lines that express significantly better resistance at both seedling and adult plant stages than Calingiri which has tsn1 only.

Organ-specific gene expression: the bHLH protein Sage provides tissue specificity to Drosophila FoxA.

FoxA transcription factors play major roles in organ-specific gene expression, regulating, for example, glucagon expression in the pancreas, GLUT2 expression in the liver, and tyrosine hydroxylase expression in dopaminergic neurons. Organ-specific gene regulation by FoxA proteins is achieved through cooperative regulation with a broad array of transcription factors with more limited expression domains. Fork head (Fkh), the sole Drosophila FoxA family member, is required for the development of multiple distinct organs, yet little is known regarding how Fkh regulates tissue-specific gene expression. Here, we characterize Sage, a bHLH transcription factor expressed exclusively in the Drosophila salivary gland (SG). We show that Sage is required for late SG survival and normal tube morphology. We find that many Sage targets, identified by microarray analysis, encode SG-specific secreted cargo, transmembrane proteins, and the enzymes that modify these proteins. We show that both Sage and Fkh are required for the expression of Sage target genes, and that co-expression of Sage and Fkh is sufficient to drive target gene expression in multiple cell types. Sage and Fkh drive expression of the bZip transcription factor Senseless (Sens), which boosts expression of Sage-Fkh targets, and Sage, Fkh and Sens colocalize on SG chromosomes. Importantly, expression of Sage-Fkh target genes appears to simply add to the tissue-specific gene expression programs already established in other cell types, and Sage and Fkh cannot alter the fate of most embryonic cell types even when expressed early and continuously.