FLOURY ENDOSPERM 6 mutations enhance the sugary phenotype caused by the loss of ISOAMYLASE1 in barley

Starch is a biologically and commercially important glucose polymer synthesized by plants as semicrystalline starch granules (SGs). Because SG morphology affects starch properties, mutants with altered SG morphology may be useful in breeding crops with desirable starch properties, including potentially novel properties. In this study, we employed a simple screen for mutants with altered SG morphology in barley (Hordeum vulgare). We isolated mutants that formed compound SGs together with the normal simple SGs in the endosperm and found that they were allelic mutants of the starch biosynthesis genes ISOAMYLASE1 (HvISA1) and FLOURY ENDOSPERM 6 (HvFLO6), encoding starch debranching enzyme and CARBOHYDRATE-BINDING MODULE 48-containing protein, respectively. We generated the hvflo6 hvisa1 double mutant and showed that it had significantly reduced starch biosynthesis and developed shrunken grains. In contrast to starch, soluble α-glucan, phytoglycogen, and sugars accumulated to higher levels in the double mutant than in the single mutants. In addition, the double mutants showed defects in SG morphology in the endosperm and in the pollen. This novel genetic interaction suggests that hvflo6 acts as an enhancer of the sugary phenotype caused by hvisa1 mutation

Related polymorphic F-box protein genes between haplotypes clustering in the BAC contig sequences around the S-RNase of Japanese pear

Most fruit trees in the Rosaceae exhibit self-incompatibility, which is controlled by the pistil S gene, encoding a ribonuclease (S-RNase), and the pollen S gene at the S-locus. The pollen S in Prunus is an F-box protein gene (SLF/SFB) located near the S-RNase, but it has not been identified in Pyrus and Malus. In the Japanese pear, various F-box protein genes (PpSFBB-α–γ) linked to the S-RNase are proposed as the pollen S candidate. Two bacterial artificial chromosome (BAC) contigs around the S-RNase genes of Japanese pear were constructed, and 649 kb around S4-RNase and 378 kb around S2-RNase were sequenced. Six and 10 pollen-specific F-box protein genes (designated as PpSFBB4-u1–u4, 4-d1–d2 and PpSFBB2-u1–u5, 2-d1–d5, respectively) were found, but PpSFBB4-α–γ and PpSFBB2-γ were absent. The PpSFBB4 genes showed 66.2–93.1% amino acid identity with the PpSFBB2 genes, which indicated clustering of related polymorphic F-box protein genes between haplotypes near the S-RNase of the Japanese pear. Phylogenetic analysis classified 36 F-box protein genes of Pyrus and Malus into two major groups (I and II), and also generated gene pairs of PpSFBB genes and PpSFBB/Malus F-box protein genes. Group I consisted of gene pairs with 76.3–94.9% identity, while group II consisted of gene pairs with higher identities (>92%) than group I. This grouping suggests that less polymorphic PpSFBB genes in group II are non-S pollen genes and that the pollen S candidates are included in the group I PpSFBB genes

Wolfberry genomes and the evolution of Lycium (Solanaceae)

AbstractWolfberry Lycium, an economically important genus of the Solanaceae family, contains approximately 80 species and shows a fragmented distribution pattern among the Northern and Southern Hemispheres. Although several herbaceous species of Solanaceae have been subjected to genome sequencing, thus far, no genome sequences of woody representatives have been available. Here, we sequenced the genomes of 13 perennial woody species of Lycium, with a focus on Lycium barbarum. Integration with other genomes provides clear evidence supporting a whole-genome triplication (WGT) event shared by all hitherto sequenced solanaceous plants, which occurred shortly after the divergence of Solanaceae and Convolvulaceae. We identified new gene families and gene family expansions and contractions that first appeared in Solanaceae. Based on the identification of self-incompatibility related-gene families, we inferred that hybridization hotspots are enriched for genes that might be functioning in gametophytic self-incompatibility pathways in wolfberry. Extremely low expression of LOCULE NUBER (LC) and COLORLESS NON-RIPENING (CNR) orthologous genes during Lycium fruit development and ripening processes suggests functional diversification of these two genes between Lycium and tomato. The existence of additional flowering locus C-like MADS-box genes might correlate with the perennial flowering cycle of Lycium. Differential gene expression involved in the lignin biosynthetic pathway between Lycium and tomato likely illustrates woody and herbaceous differentiation. We also provide evidence that Lycium migrated from Africa into Asia, and subsequently from Asia into North America. Our results provide functional insights into Solanaceae origins, evolution and diversification.</jats:p