Post-pollination prefertilization drops affect germination rates of heterospecific pollen in larch and Douglas-fir.

Pollen of larch (Larix × marschlinsii) and Douglas-fir (Pseudotsuga menziesii) was used in homospecific and heterospecific crosses. Germination of heterospecific pollen in ovulo was reduced in post-pollination prefertilization drops. This provides evidence of selection against foreign pollen by open-pollinated exposed ovules in these two sister taxa, which share the same type of pollination mechanism. Of the other prezygotic stages in pollen-ovule interactions, uptake of pollen by stigmatic hairs did not show any selection. Pollen tube penetration of the nucellus was similar for hetero- and homospecific pollen tubes, but heterospecific tubes only delivered gametes in one cross. To test for differences in the post-pollination prefertilization drops of each species, drops were gathered and analysed. Glucose and fructose were present in similar amounts in Douglas-fir and larch, while sucrose was found in larch only. Other carbohydrates such as xylose and melezitose were species-specific. In P. menziesii, sucrose is absent due to its conversion to glucose and fructose by apoplastic invertases. In contrast, Larix × marschlinsii drops have sucrose because they lack apoplastic invertases. The presence of invertase activity shows that the composition of gymnosperm post-pollination prefertilization drops is not static but dynamic. Drops of these two species also differed in their calcium concentrations.

Acidification-dependent activation of CD1d-restricted natural killer T cells is intact in cystic fibrosis.

CD1d-restricted natural killer T (NKT) cells are emerging as critical regulators of the immune response to infectious agents, including Pseudomonas aeruginosa; and therapies to augment NKT-cell activation may represent a novel approach to treat chronic, antibiotic-resistant bacterial infections. We examined the capacity of dendritic cells (DCs) from people with cystic fibrosis (CF) to activate NKT cells. Our study was motivated by three lines of evidence: (i) NKT cells play a critical role in clearing P. aeruginosa infection; (ii) activation of NKT cells requires acidification-dependent processing of glycolipid antigens within the endolysosomal compartment; and (iii) endolysosomal acidification may be reduced in CF. We demonstrated that NKT-cell activation was dependent upon intact organelle acidification as inhibitors of the vacuolar (H(+))-ATPases prevented DCs from activating NKT cells with two glycolipid antigens, alpha-galactosylceramide and galactose-galactosylceramide. In contrast, cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel dysfunction had no significant biological impact on the capacity of DCs to activate NKT cells. Dendritic cells from subjects with CF and DCs treated with the thiazolidinone CFTR(inh)-172 inhibitor showed no reduction in their ability to activate NKT cells. Based on these data, we find no evidence for an inherent defect in glycolipid antigen presentation to NKT cells in CF subjects.