The discovery of unbranched, monocephalic natural variants was pivotal for the domestication of sunflower (Helianthus annuus L.). The branching locus (B), one of several loci apparently targeted by aboriginal selection for monocephaly, pleiotropically affects plant, seed and capitula morphology and, when segregating, confounds the discovery of favorable alleles for seed yield and other traits. The present study was undertaken to gain deeper insights into the genetics of branching and seed traits affected by branching. We produced an unbranched hybrid testcross recombinant inbred line (TC-RIL) population by crossing branched (bb) and unbranched (BB) RILs to an unbranched (BB) tester. The elimination of branching concomitantly eliminated a cluster of B-linked seed trait quantitative trait loci (QTL) identified by RIL per se testing. We identified a seed oil content QTL linked in repulsion and a 100-seed weight QTL linked in coupling to the B locus and additional unlinked QTL, previously masked by B-locus pleiotropy. Genomic segments flanking the B locus harbor multiple loci for domestication and post-domestication traits, the effects of which are masked by B-locus pleiotropy in populations segregating for branching and can only be disentangled by genetic analyses in unbranched populations. QTL analyses of NILs carrying wild B alleles substantiated the pleiotropic effects of the B locus. The effect of the B locus on branching was masked by the effects of wild alleles at independent branching loci in hybrids between monocephalic domesticated lines and polycephalic wild ecotypes; hence, the B locus appears to be necessary, but not sufficient, for monocephaly in domesticated sunflower.

The genetically related assemblages of the intestinal protozoa parasite Giardia lamblia are morphologically indistinguishable and are often derived from specific hosts. The Giardia assemblages are separated by large genetic distances, which might account for their relevant biological and pathogenic differences. In this work, we analyzed the RNAs cargo released into exosomal-like vesicles (ElVs) by the assemblages A and B, which differentially infect humans, and the assemblage E, which infects hoofed animals. The RNA sequencing analysis revealed that the ElVs of each assemblage contained distinct small RNA (sRNA) biotypes, suggesting a preference for specific packaging in each assemblage. These sRNAs were classified into three categories, ribosomal-small RNAs (rsRNAs), messenger-small RNAs (msRNAs), and transfer-small RNAs (tsRNAs), which may play a regulatory role in parasite communication and contribute to host-specificity and pathogenesis. Uptake experiments showed, for the first time, that ElVs were successfully internalized by the parasite trophozoites. Furthermore, we observed that the sRNAs contained inside these ElVs were first located below the plasma membrane but then distributed along the cytoplasm. Overall, the study provides new insights into the molecular mechanisms underlying the host-specificity and pathogenesis of G. lamblia and highlights the potential role of sRNAs in parasite communication and regulation.

Eight isozyme systems were used in this study: acid phosphatase (ACP), alcohol dehydrogenase (ADH), esterase (EST), glutamate dehydrogenase (GDH), malate dehydrogenase (MDH), phosphoglucoisomerase (PGI), 6-phosphogluconate dehydrogenase (PGD), and phosphoglucomutase (PGM). The polymorphism of these enzyme systems was studied in 25 elite inbred lines. A total of 19 loci were identified, but only eight of them were polymorphic in the germplasm tested. The polymorphic index for the eight informative markers ranged from 0.08 to 0.57, with a mean value of 0.36. Five isozyme loci were mapped in F 2:3 populations with existing RFLP data. Est-1, Gdh-2 and Pgi-2 were mapped to linkage groups 3, 14 and 9, respectively. As in previous reports, an ACP locus and a PGD locus were found to be linked, both located in linkage group 2 of the public sunflower map.