QTL in mega-environments: II. Agronomic trait QTL co-localized with seed yield QTL detected in a population derived from a cross of high-yielding adapted × high-yielding exotic soybean lines

Seed yield mega-environment-universal and specific QTL (QTL_U and QTL_SP, respectively) linked to Satt100, Satt130, Satt162, Satt194, Satt259 Satt277 and Sat_126, have been identified in a population derived from a cross between a Chinese and a Canadian soybean [Glycine max (L.) Merrill] elite line. The variation observed in yield could be the consequence of the variation of agronomic traits. Yield-component traits have been reported in the literature, but a better understanding of their impact at the molecular level is still lacking. Therefore, the objectives of this study were to identify traits correlated with yield and to determine if the yield QTL_U and QTL_SP were co-localized with QTL_U and QTL_SP associated with an agronomic trait. A recombinant inbred line (RIL) population was developed from a cross between a high-yielding adapted Canadian and a high-yielding exotic Chinese soybean elite line. The RIL were evaluated in multiple environments in China and Canada during the period from 2004 to 2006. Four yield QTL_U, tagged by markers Satt100, Satt277, Satt162 and Sat_126, were co-localized with a QTL associated with an agronomic trait, behaving as either QTL_U or QTL_SP for the agronomic trait. For example, the yield QTL_U, tagged by marker Satt100 was associated also with 100 seed weight, pods per plant, pods per node, plant height, R1, R5, R8, oil content and protein content in all Canadian environments, but only with pods per plant, pods per node, plant height, R1, R5, R8 and oil content in two or more Chinese environments. No agronomic traits QTL were co-localized with the yield QTL_U tagged by the marker Satt139 or the yield QTL_SP tagged by Satt259, suggesting a physiological basis of the yield in these QTL. The results suggest that a successful introgression of crop productivity alleles from plant introductions into an adapted germplasm could be facilitated by the use of both the QTL_U and QTL_SP because each type of QTL contributed either directly or indirectly through yield-component traits to seed yield of RILs.     

QTL in mega-environments: I. Universal and specific seed yield QTL detected in a population derived from a cross of high-yielding adapted × high-yielding exotic soybean lines

Modern soybean [(Glycine max (L.) Merrill] breeding programs rely primarily on the use of elite × elite line crosses to develop high-yielding cultivars. Favorable alleles for traits of interest have been found in exotic germplasm but the successful introduction of such alleles has been hampered by the lack of adaptation of the exotic parent to local mega-environment and difficulties in identifying superior progeny from elite × exotic crosses. The objective of this study was to use a population derived from a cross between an adapted and an exotic elite line to understand the genetic causes underlying adaptation to two mega-environments (China and Canada). A cross between a high-yielding Canadian cultivar ‘OAC Millennium’ and an elite Chinese cultivar ‘Heinong 38’ was performed to develop a recombinant inbred line (RIL) population. The RIL population was evaluated in China and Canada in multiple environments from 2004 to 2006. Significant variation for seed yield was observed among the RILs in both the Chinese and Canadian environment. Individual RILs performed differently between the Chinese and Canadian environments suggesting differential adaptation to intercontinental mega-environments. Seven seed yield quantitative trait loci (QTL) were identified of which five were mega-environment universal QTL (linked to markers Satt100, Satt162, Satt277, Sat_126, and the interval of Satt139-Sat_042) and two were mega-environment-specific QTL (at marker intervals, Satt194-SOYGPA and Satt259-Satt576). Seed yield QTL located near Satt277 has been confirmed and new QTL have been identified explaining between 9 and 37% of the phenotypic variation in seed yield. The QTL located near Satt100 explained the greatest amount of variation ranging from 18 to 37% per environment. Broad sense heritability ranged from 89 to 64% among environments. Epistatic effects have been identified in both mega-environments with pairs of markers explaining between 9 and 14% of the phenotypic variation in seed yield. An improved understanding of the type of QTL action as either universal or mega-environment-specific QTL as well as their interaction may facilitate the development of strategies to introgress specific high-yielding alleles from Chinese to North American germplasm and vice versa to sustain efforts in breeding of high-yielding soybean cultivars.     

The Effects of Neuraminidase and Gangliosides on Ovarian LH/hCG Receptors During Rat Development

Ovaries of neonatal rats are not endowed with specific LH/hCG receptors up to 6–8 days of age. Treatment of ovarian membranes of the neonatal rat with neuraminidase results in a specific binding of radioactively labeled hCG, while an increase of hormone binding is observed after neuraminidase treatment of ovarian membranes of the 21-day-old rat. These changes in hormone receptor sites in the ovary are dependent on the neuraminidase concentration used and are due to a receptor with a dissociation constant (K_D) of about 10⁻⁹ M. The K_D of the receptor in the LH/hCG sensitive ovary without neuraminidase treatment is about 10⁻¹⁰ M. These results indicate the presence of two different LH/hCG receptors in the ovarian membrane. The unmasking effect of neuraminidase onto LH/hCG receptors indicate that ganglioside-like structures are responsible for the masking of receptors in the neonatal, insensitive rat ovary and also in the 21-day-old sensitive ovary. Ganglioside preparations are able to inhibit the binding, and the fractionation of ovary gangliosides results in a fraction with a rather high inhibition potency of LH/hCG binding to the receptor. It is hypothesized that the masked receptors in the sensitive period represent a store of receptors for the reconstitution of the ovarian cells with active receptors after internalization of the hormone-receptor complex. Thus the masking of the receptors in the early postnatal rat ovary could be a prerequisite for the female differentiation of hypothalamic centers. The observed neuraminidase effect in vitro could reflect a physiologic situation. Neuraminidase was found in the ovary, and during early postnatal development the neuraminidase activity pattern coincides with that of the ovarian LH/hCG receptor changes.     

Two new stoloniferous species of Viola (Violaceae) from China

Two new stoloniferous species of Viola (Violaceae) from southern China are described and illustrated. Viola nitida is recognizably different from V. fargesii as the plant is evergreen and glabrous throughout, the leaf blade adaxially nitid, base cuneate or shallowly cordate, and margin serrate. Viola maoershanensis is different from V. diffusa as the leaf blade is serrate, base cordate and not decurrent to petiole, the petiole wingless, the flowers larger, the petals bluish violet or pinkish white, and the lower petal obtuse at the apex. The chromosome numbers of the two new species were counted as 2n = 24 (V. nitida) and 2n = 44 (V. maoershanensis). The taxonomic positions of the two species are discussed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 349–356.     

Cloning and expression of an anti-LDL(-) single-chain variable fragment,and its inhibitory effect on experimental atherosclerosis

The in vivo modified forms of low-density lipoprotein (LDL) are important for the formation of foam cells and as mediators of the immuno-inflammatory process involved in the progression of atherosclerosis. Electronegative LDL, LDL(-), is a LDL subfraction with pro-inflammatory properties that is present in human blood. To investigate possible atheroprotective effects, an anti-LDL(-) single-chain variable fragment (scFv) was expressed in the methylotrophic yeast Pichia pastoris and its activity was evaluated in vitro against macrophages and in experimental atherosclerosis in Ldlr^-/- mice. The recombinant 2C7 scFv was produced in a yield of 9.5 mg of protein/L. The specificity and affinity of purified 2C7 scFv against LDL(-) was confirmed by ELISA. To assess the activity of 2C7 scFv on foam cell formation, RAW 264.7 macrophages were exposed to LDL(-) in the presence or absence of 2C7 scFv. The 2C7 scFv inhibited the uptake of LDL(-) by macrophages in a dose-dependent manner, and internalization of LDL(-) by these cells was found to be mediated by the CD36 and CD14 receptor. In addition, compared with untreated cells, lipid accumulation in macrophages was decreased, and the expression of Cd36, Tlr-4 and Cox-2 was downregulated in macrophages treated with 2C7 scFv. Importantly, compared with untreated mice, the treatment of Ldlr^-/- mice with 2C7 scFv decreased the atherosclerotic lesion area at the aortic sinus. In conclusion, our data show that 2C7 scFv inhibits foam cell formation and atherosclerotic plaque development by modulating the expression of genes relevant to atherogenesis. These results encourage further use of this antibody fragment in the development of new therapeutic strategies that neutralize the pro-atherogenic effects of LDL(-).