An F4:5 population of 490 recombinant inbred lines (RILs) from the cross Apo/2 Swarna was used to detect quantitative trait loci (QTL) with large effects on grain yield under drought stress using ...bulk-segregant analysis (BSA). Swarna is an important rainfed lowland rice variety grown on millions of hectares in Asia, but is highly susceptible to drought and aerobic soil conditions. Apo is an aerobic-adapted variety with moderate tolerance to drought. Two rice microsatellite (RM) markers, RM324, and RM416, located on chromosomes 2 and 3, respectively, were shown via BSA to be strongly associated with yield under lowland drought stress. The effects of these QTL were tested in a total of eight hydrological environments over a period of 3 years. The QTL linked to RM416 (DTY 3.1) had a large effect on grain yield under severe lowland drought stress, explaining about 31% of genetic variance for the trait (P < 0.0001). It also explained considerable variance for yield under mild stress in lowland conditions and aerobic environments. To our knowledge this is the first reported QTL that has a large effect on yield in both lowland drought and aerobic environments. The QTL linked to RM324 (DTY 2.1.) had a highly significant effect on grain yield in lowland drought stress (R 2 = 13?16%) and in two aerobic trials. The effect of these QTL on grain yield was verified to be not mainly due to phenology differences. Effects of DTY 3.1. on yield under stress have been observed in several other rice mapping populations studied at IRRI. Results of this study indicate that BSA is an effective method of identifying QTL alleles with large effects on rice yield under severe drought stress. The Apo alleles for these large-effect QTL for grain yield under drought and aerobic conditions may be immediately exploited in marker-assisted-breeding to improve the drought tolerance of Swarna
A large-effect QTL for grain yield under drought conditions (qtl12.1) was reported in a rice mapping population derived from Vandana and Way Rarem. Here, we measured the effect of qtl12.1 on grain ...yield and associated traits in 21 field trials: ten at IRRI in the Philippines and 11 in the target environment of eastern India. The relative effect of the QTL on grain yield increased with increasing intensity of drought stress, from having no effect under well-watered conditions to having an additive effect of more than 40% of the trial mean in the most severe stress treatments. The QTL improved grain yield in nine out of ten direct-seeded upland trials where drought stress was severe or moderate, but no effect was measured under well-watered aerobic conditions or under transplanted lowland conditions. These trials confirm that qtl12.1 has a large and consistent effect on grain yield under upland drought stress conditions, in a wide range of environments.
Mapping quantitative traits has brought about a renaissance in the field of quantitative genetics. A better understanding of several biometric concepts has emerged with the availability of ...progressively saturating molecular maps. The authors have tagged two agronomically complex traits viz., root morphological traits and grain yield under two contrasting moisture regimes in IR64/Azucena doubled haploid population. Biometrical investigations were undertaken simultaneously. Genetic correlation revealed highly significant linear relation of grain yield with root morphology viz., root length, root thickness in a low-moisture stress condition, which was absent in well-watered environment indicating that better root system was advantageous in a moisture stress environment. However, correlations could arise through pleiotrophy, linkage or environment causes, and hence, be misleading on many occasions. The authors investigated reasons for this correlation by mapping quantitative traits. The two complex traits were mapped onto rice linkage map with 260 markers (threshold LOD 2.00). Thirty-six loci were detected for grain yield and related traits in low-moisture stress, well watered and the mean environments. The region of chromosome 3 (RM231-RZ329) showed congruence for root volume, root dry weight, straw weight and days to flowering. Except these, the position of the rest of the root and shoot related traits were separate. Indicating that irrespective of the moisture status, quantitative trait loci governing root morphological traits and grain yield to be distinct. Grain yield and root morphological traits were neither linked nor pleiotrophic to each other. Thus, even though correlations exists, trait loci were distinct. Hence, it is possible to combine them favorably for enhanced drought resistance using innovative plant breeding and mapping strategies
We have previously demonstrated that TGFβ Inducible Early Gene-1 (TIEG1), also known as KLF10, plays important roles in mediating skeletal development and homeostasis in mice. TIEG1 has also been ...identified in clinical studies as one of a handful of genes whose altered expression levels or allelic variations are associated with decreased bone mass and osteoporosis in humans. Here, we provide evidence for the first time that TIEG1 is involved in regulating the canonical Wnt signaling pathway in bone through multiple mechanisms of action. Decreased Wnt signaling in the absence of TIEG1 expression is shown to be in part due to impaired β-catenin nuclear localization resulting from alterations in the activity of AKT and GSK-3β. We also provide evidence that TIEG1 interacts with, and serves as a transcriptional co-activator for, Lef1 and β-catenin. Changes in Wnt signaling in the setting of altered TIEG1 expression and/or activity may in part explain the observed osteopenic phenotype of TIEG1 KO mice as well as the known links between TIEG1 expression levels/allelic variations and patients with osteoporosis.
Sustained calcium signaling induces a state of anergy or antigen unresponsiveness in T cells, mediated through calcineurin and the transcription factor NFAT. We show here that Ca(2+)-induced anergy ...is a multistep program that is implemented at least partly through proteolytic degradation of specific signaling proteins. Calcineurin increased mRNA and protein of the E3 ubiquitin ligases Itch, Cbl-b and GRAIL and induced expression of Tsg101, the ubiquitin-binding component of the ESCRT-1 endosomal sorting complex. Subsequent stimulation or homotypic cell adhesion promoted membrane translocation of Itch and the related protein Nedd4, resulting in degradation of two key signaling proteins, PKC-theta and PLC-gamma1. T cells from Itch- and Cbl-b-deficient mice were resistant to anergy induction. Anergic T cells showed impaired calcium mobilization after TCR triggering and were unable to maintain a mature immunological synapse, instead showing late disorganization of the outer ring containing lymphocyte function-associated antigen 1. Our results define a complex molecular program that links gene transcription induced by calcium and calcineurin to a paradoxical impairment of signal transduction in anergic T cells.
Understanding the genetics of field-based tolerance to high iron-associated (HIA) stress in rice can accelerate the development of new varieties with enhanced yield performance in West African ...lowland ecosystems. To date, few field-based studies have been undertaken to rigorously evaluate rice yield performance under HIA stress conditions. In this study, two NERICA ×
bi-parental rice populations and one
diversity panel consisting of 296 rice accessions were evaluated for grain yield and leaf bronzing symptoms over multiple years in four West African HIA stress and control sites. Mapping of these traits identified a large number of QTLs and single nucleotide polymorphisms (SNPs) associated with stress tolerance in the field. Favorable alleles associated with tolerance to high levels of iron in anaerobic rice soils were rare and almost exclusively derived from the
subpopulation, including the most favorable alleles identified in NERICA varieties. These findings highlight the complex genetic architecture underlying rice response to HIA stress and suggest that a recurrent selection program focusing on an expanded
genepool could be productively used in combination with genomic selection to increase the efficiency of selection in breeding programs designed to enhance tolerance to this prevalent abiotic stress in West Africa.
Drought stress is the most important abiotic factor limiting upland rice yields. Identification of quantitative trait loci (QTL) conferring improved drought resistance may facilitate breeding ...progress. We previously mapped a QTL with a large effect on grain yield under severe drought stress (
qtl12.1) in the Vandana/Way Rarem population. In the current paper, we present results from a series of experiments investigating the physiological mechanism(s) by which
qtl12.1 affects grain yield under drought conditions. We performed detailed plant water status measurements on a subset of lines having similar crop growth duration but contrasting genotypes at
qtl12.1 under field (24 genotypes) and greenhouse (14 genotypes) conditions. The Way Rarem-derived allele of
qtl12.1 was confirmed to improve grain yield under drought mainly through a slight improvement (7%) in plant water uptake under water-limited conditions. Such an apparently small increase in water uptake associated with this allele could explain the large effect on yield observed under field conditions. Our results suggest that this improvement of plant water uptake is likely associated with improved root architecture.
Antigen-specific immunotolerance limits the expansion of self-reactive T cells involved in autoimmune diseases. Here, we show that the E3 ubiquitin ligase Cbl-b is upregulated in T cells after ...tolerizing signals. Loss of Cbl-b in mice results in impaired induction of T cell tolerance both in vitro and in vivo. Importantly, rechallenge of Cbl-b mutant mice with the tolerizing antigen results in massive lethality. Moreover, ablation of Cbl-b resulted in exacerbated autoimmunity. Mechanistically, loss of Cbl-b rescues reduced calcium mobilization of anergic T cells, which was attributed to Cbl-b-mediated regulation of PLCγ-1 phosphorylation. Our results show a critical role for Cbl-b in the regulation of peripheral tolerance and anergy of T cells.
A large-effect QTL for grain yield under drought conditions (qtl12.1) was reported in a rice mapping population derived from Vandana and Way Rarem. Here, we measured the effect of qtl12.1 on grain ...yield and associated traits in 21 field trials: ten at IRRI in the Philippines and 11 in the target environment of eastern India. The relative effect of the QTL on grain yield increased with increasing intensity of drought stress, from having no effect under well-watered conditions to having an additive effect of more than 40% of the trial mean in the most severe stress treatments. The QTL improved grain yield in nine out of ten direct-seeded upland trials where drought stress was severe or moderate, but no effect was measured under well-watered aerobic conditions or under transplanted lowland conditions. These trials confirm that qtl12.1 has a large and consistent effect on grain yield under upland drought stress conditions, in a wide range of environments.
Late leaf spot (LLS), caused by
Phaeoisariopsis personata
, is an important foliar fungal disease of groundnut (
Arachis hypogaea
L.), which causes significant economic losses globally to the crop. ...Inheritance of resistance to LLS disease was studied in three crosses and their reciprocals involving two resistant interspecific derivatives and a susceptible cultivar to refine strategy for LLS resistance breeding. The traits associated with LLS resistance, measured both in the field and under controlled conditions were studied following generation mean analysis. Results suggested that resistance to LLS is controlled by a combination of both, nuclear and maternal gene effects. Among nuclear gene effects, additive effect controlled majority of the variation. In JL 24 × ICG 11337 cross and its reciprocal only additive effects were important, while in JL 24 × ICG 13919 cross and its reciprocal, both additive and dominance effects contributed to the variation. Among digenic epistatic effects, additive × dominance interactions were significant. Additive–maternal effects were significant in both the crosses, while dominance–maternal effects also contributed to the variation in the crosses between the parents, JL 24 and ICG 13919. Due to significant contribution of additive effects of both nuclear and maternal inheritance to resistance to LLS, the parent, ICG 11337 would be a good donor in breeding programs. It would be worthwhile to use the resistance donor as female parent to tap maternal effects of resistance to LLS. Disease score is the best selection criterion in the field for use in breeding programs because of its high heritability and ease in measurement.
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