Gal Sapir

The RHV region of S-RNase in the European pear (Pyrus communis) is not required for the determination of specific pollen rejection

In the gametophytic self-incompatibility system, growth of self-pollen tubes in the style is inhibited in a haplotype-specific manner by S-RNase. The mechanism by which S-RNase confers its specificity is unknown. However, a hypervariable region (RHV in Rosaceae and HVa-HVb in Solanaceae) that differs among the many cloned S-RNase alleles has been proposed to be involved in conferring the S-haplotype specificity of the S-RNase. Region swapping experiments between S-RNases and crystallography of the enzyme support this assumption. However, the deduced amino acid sequences of Sn-RNase and Si-RNase alleles from the European pear (Pyrus communis) were recently found to have an identical RHV. In the present study it is shown that Sn-RNase does not prevent fertilization by Si-pollen haplotype, thus presenting a case in which RHV is not required for the determination of specific pollen rejection by S-RNase, and implying that other regions in the enzyme may be sufficient for this specificity.

Multiple introduction of honeybee colonies increases cross-pollination, fruit-set and yield of ‘Black Diamond’ Japanese plum (Prunus salicina Lindl.)

Summary Japanese plum (Prunus salicina Lindl.) belongs to the Rosaceae family, which carries the S-RNase-mediated gametophytic self-incompatibility system, which prevents self-fertilisation, and thus promotes out-crossing. The plum cultivar ‘Black Diamond’® has become, one of the most important cultivars in Israel in the last decade, yet its yield is low in comparison with its known potential. Honeybees (Apis mellifera) are the most important pollinators for plums and several studies have demonstrated an apparent relationship between the number of honeybees and the size of the fruit crop. Therefore, in this study, we focussed on improving bee management in a ‘Black Diamond’ orchard. In four consecutive years of experiments, we examined the effects of increasing the density of bee colonies, and of making multiple introductions of colonies, on honeybee activity and on their effectiveness as pollinators of ‘Black Diamond’. We showed that four separate introductions, each of 0.625 colonies ha–1, every 2 – 3 d from 10% full bloom to 3 d after full bloom, with a total density of only 2.5 colonies ha–1, resulted in the greatest level of fruit set.

Biochemical phosphates observed using hyperpolarized 31 P in physiological aqueous solutions

The dissolution-dynamic nuclear polarization technology had previously enabled nuclear magnetic resonance detection of various nuclei in a hyperpolarized state. Here, we show the hyperpolarization of 31P nuclei in important biological phosphates (inorganic phosphate and phosphocreatine) in aqueous solutions. The hyperpolarized inorganic phosphate showed an enhancement factor >11,000 (at 5.8 T, 9.3% polarization) in D2O (T1 29.4 s). Deuteration and the solution composition and pH all affected the lifetime of the hyperpolarized state. This capability opens up avenues for real-time monitoring of phosphate metabolism, distribution, and pH sensing in the live body without ionizing radiation. Immediate changes in the microenvironment pH have been detected here in a cell-free system via the chemical shift of hyperpolarized inorganic phosphate. Because the 31P nucleus is 100% naturally abundant, future studies on hyperpolarized phosphates will not require expensive isotope labeling as is usually required for hyperpolarization of other substrates.Real-time monitoring of phosphate metabolism and distribution in the live body without ionizing radiation is highly desirable. Here, the authors show dissolution-dynamic nuclear polarization technology can enable nuclear magnetic resonance detection of hyperpolarized 31P of important biological phosphates in aqueous solutions.

Real-time ex-vivo measurement of brain metabolism using hyperpolarized [1- 13 C]pyruvate

The ability to directly monitor in vivo brain metabolism in real time in a matter of seconds using the dissolution dynamic nuclear polarization technology holds promise to aid the understanding of brain physiology in health and disease. However, translating the hyperpolarized signal observed in the brain to cerebral metabolic rates is not straightforward, as the observed in vivo signals reflect also the influx of metabolites produced in the body, the cerebral blood volume, and the rate of transport across the blood brain barrier. We introduce a method to study rapid metabolism of hyperpolarized substrates in the viable rat brain slices preparation, an established ex vivo model of the brain. By retrospective evaluation of tissue motion and settling from analysis of the signal of the hyperpolarized [1-13C]pyruvate precursor, the T1s of the metabolites and their rates of production can be determined. The enzymatic rates determined here are in the range of those determined previously with classical biochemical assays and are in agreement with hyperpolarized metabolite relative signal intensities observed in the rodent brain in vivo.

Author Correction: Biochemical phosphates observed using hyperpolarized 31 P in physiological aqueous solutions

The original version of the Supplementary Information associated with this Article contained an error in Supplementary Figure 2 and Supplementary Figure 5 in which the 31P NMR spectral lines were missing. The HTML has been updated to include a corrected version of the Supplementary Information.