Loss-of-function mutation of soybean R2R3 MYB transcription factor reduces flavone content and dilutes tawny pubescence color

Background Pubescence color of soybean is controlled by two genes, T and Td. In the presence of a dominant T allele, dominant and recessive alleles of the Td locus generate tawny and light tawny (or near-gray) pubescence, respectively. Flavones, responsible for pubescence color, are catalyzed by two copies of flavone synthase II genes (FNS II-1 and FNS II-2). This study was conducted to map and clone the Td gene. Results Genetic and linkage analysis using an F2 population and F3 families derived from a cross between a Clark near-isogenic line with light tawny pubescence (genotype: TT tdtd) and a Harosoy near-isogenic line with tawny pubescence (TT TdTd) revealed a single gene for pubescence color around the end of chromosome 3. Genome sequence alignment of plant introductions revealed an association between premature stop codons in Glyma.03G258700 (R2R3 MYB transcription factor) and recessive td allele. Cultivars and lines having near-gray or light tawny pubescence and a gray pubescence cultivar with td allele had premature stop codons in the gene. These results suggest that Glyma.03G258700 corresponds to the Td gene. It was predominantly expressed in pubescence. Compared to a tawny pubescence line, a near-isogenic line with td allele produced extremely small amounts of transcripts of Glyma.03G258700, FNS II-1, and FNS II-2 in pubescence. The promoter of FNS II-1 and FNS II-2 shared cis-acting regulatory elements for binding of MYB proteins. These results suggest that the wild-type of Glyma.03G258700 protein binds to the promoter of FNS II genes and upregulates their expression, resulting in increased flavone content and deeper pubescence color. In contrast, mutated Glyma.03G258700 protein fails to upregulate the expression of FNS II genes, resulting in decreased flavone content and dilute pubescence color. Conclusions This study revealed that soybean Glyma.03G258700 encoding the R2R3 MYB transcription factor corresponds to the Td gene. The wild type of MYB protein binds to the promoter of FNS II genes and upregulates their expression, resulting in higher flavone content and deeper pubescence color. Loss-of-function mutation of the gene fails to promote expression of FNS II genes, resulting in lower flavone content and dilute pubescence color.

Eumelanin and pheomelanin are predominant pigments in bumblebee (Apidae: Bombus) pubescence

Background Bumblebees (Hymenoptera: Apidae: Bombus) are well known for their important inter- and intra-specific variation in hair (or pubescence) color patterns, but the chemical nature of the pigments associated with these patterns is not fully understood. For example, though melanization is believed to provide darker colors, it still unknown which types of melanin are responsible for each color, and no conclusive data are available for the lighter colors, including white. Methods By using dispersive Raman spectroscopy analysis on 12 species/subspecies of bumblebees from seven subgenera, we tested the hypothesis that eumelanin and pheomelanin, the two main melanin types occurring in animals, are largely responsible for bumblebee pubescence coloration. Results Eumelanin and pheomelanin occur in bumblebee pubescence. Black pigmentation is due to prevalent eumelanin, with visible signals of additional pheomelanin, while the yellow, orange, red and brown hairs clearly include pheomelanin. On the other hand, white hairs reward very weak Raman signals, suggesting that they are depigmented. Additional non-melanic pigments in yellow hair cannot be excluded but need other techniques to be detected. Raman spectra were more similar across similarly colored hairs, with no apparent effect of phylogeny and both melanin types appeared to be already used at the beginning of bumblebee radiation. Discussion We suggest that the two main melanin forms, at variable amounts and/or vibrational states, are sufficient in giving almost the whole color range of bumblebee pubescence, allowing these insects to use a single precursor instead of synthesizing a variety of chemically different pigments. This would agree with commonly seen color interchanges between body segments across Bombus species.

Characterization of Spontaneous Crosses between Clearfield Rice (Oryza sativa) and Red Rice (Oryza sativa)

Experiments were conducted to determine the inheritance of resistance in crosses between imazethapyr-resistant rice and red rice. Past experiments on red rice control, using the Clearfield rice technology, resulted in outcrossing between Clearfield rice and Stuttgart strawhull red rice. The F2 generation of these spontaneous crosses were characterized with respect to inheritance of imazethapyr resistance, leaf color and leaf pubescence, and seed shattering, pubescence, color, and size. Agronomic traits of hybrids were also observed in relation to their parents. To determine the segregation of resistance among F2 phenotypes, the response of three- to four-leaf plants to imazethapyr was scored 3 wk after application as resistant (R, no imazethapyr symptoms), susceptible (S, death of plants), or intermediate (I, stunted plants). R, I, and S phenotypes segregated in a 1:2:1 ratio in the F2 generation. Two- or three-gene inheritance was documented for leaf and seed characteristics. A wide range in onset of flowering (70 to 130 d after planting) was observed in F2 families, although 6% of the plants did not flower during the growing season. F2 plants were taller and had more tillers than any of their parents. Resistance to imazethapyr is associated with a single, incompletely dominant allele.