Biomass formation and sugar release efficiency of Populus modified by altered expression of a NAC transcription factor

Woody biomass is an important feedstock for biofuel production. Manipulation of wood properties that enable efficient conversion of biomass to biofuel reduces cost of biofuel production. Wood cell wall composition is regulated at several levels that involve expression of transcription factors such as wood-/secondary cell wall- associated NAC domains (WND or SND). In Arabidopsis thaliana, SND1 regulates cell wall composition through activation of its down-stream targets such as MYBs. The functional aspects of SND1 homologs in the woody Populus have been studied through transgenic manipulation. In this study, we investigated the role of PdWND1B, Populus SND1 sequence ortholog, in wood formation using transgenic manipulation through over-expression or silencing under the control of a vascular-specific 4-coumarate-CoA ligase (4CL) promoter. As compared to control plants, PdWND1B-RNAi plants were shorter in height, with significantly reduced stem diameter and dry biomass, whereas there were no significant differences in growth and productivity of PdWND1B over-expression plants. Conversely, PdWND1B over-expression lines showed a significant reduction in cellulose and increase in lignin content, whereas there was no significant impact on lignin content of down-regulated lines. Stem carbohydrate composition analysis revealed a decrease in glucose, mannose, arabinose, and galactose, but an increase in xylose in the over-expression lines. Transcriptome analysis revealed upregulation of several downstream transcription factors and secondary cell wall related structural genes in the PdWND1B over-expression lines that corresponded to significant phenotypic changes in cell wall chemistry observed in PdWND1B overexpression lines. Relative to the control, glucose release and ethanol production from stem biomass was significantly reduced in over-expression lines but appeared enhanced in the RNAi lines. Our results show that PdWND1B is an important factor determining biomass productivity, cell wall chemistry and its conversion to biofuels in Populus.

Variation in relaxation of non-photochemical quenching in a soybean nested association mapping panel as a potential source for breeding improved photosynthesis

Improving the efficiency of crop photosynthesis has the potential to increase yields. Genetic manipulation showed photosynthesis can be improved in Tobacco by speeding up relaxation of photoprotective mechanisms, known as non-photochemical quenching (NPQ), during high to low light transitions. However, it is unclear if natural variation in NPQ relaxation can be exploited in crop breeding programs. To address this issue, we measured NPQ relaxation in the 41 parents of a soybean NAM population in field experiments in Illinois during 2018 and 2019. There was significant variation in amount and rate of fast, energy dependent quenching (qE) between genotypes. However, strong environmental effects led to a lack of correlation between values measured over the two growing season, and low broad-sense heritability estimates (< 0.3). These data suggest that either improvements in screening techniques, or transgenic manipulation, will be required to unlock the potential for improving the efficiency of NPQ relaxation in soybean.Table of Abbreviations

Callus induction of tartary buckwheat and enhancement of its flavonoids via FtCHS1 overexpression

Tartary buckwheat (Fagopyrum tataricum), a popular and traditional health care-related cereal, has recently been the focus of research because of its metabolic regulation of flavonoids. Elicitingtissues in vitroculture is an effective way to explore flavonoid biosynthesis mechanisms in tartary buckwheat. In the present study, we developed an in vitro genetic transformation system using the tartary buckwheat variety ‘Xiqiao No. 2’. The results showed thattherate of callus induced from hypocotylexplants on Murashige and Skoog (MS) medium containing 0.8 mg/L 6-BA and 3.5 mg/L 2,4-D was 100%. Much greater amounts of calli could then be obtained by repeated subculture on MS medium supplemented with 3.0 mg/L 6-BA and 1.0 mg/L KT. Furthermore, transgenic calli expressing the FtCHS1 gene were obtained viaAgrobacterium-mediatedtransformation. Overexpressing FtCHS1 in tartary buckwheat callus led tothe marked promotion of flavonol (P<0.01) and anthocyanin accumulation (P<0.05) due to the dramatic upregulation of the transcription of FtCHI, FtCHS2, FtFLS1, FtFLS2, FtFLS3 and FtDFR1, the genes of key enzymes involved in the flavonol and anthocyanin biosynthesis pathways (P < 0.01). This study provides solid support for further transgenic manipulation of calli as part of a system for regenerating tartary buckwheat.

Callus induction of tartary buckwheat and enhancement of its flavonoids via FtCHS1 overexpression

Tartary buckwheat (Fagopyrum tataricum), a popular and traditional health care-related cereal, has recently been the focus of research because of its metabolic regulation of flavonoids. Elicitingtissues in vitroculture is an effective way to explore flavonoid biosynthesis mechanisms in tartary buckwheat. In the present study, we developed an in vitro genetic transformation system using the tartary buckwheat variety ‘Xiqiao No. 2’. The results showed thattherate of callus induced from hypocotylexplants on Murashige and Skoog (MS) medium containing 0.8 mg/L 6-BA and 3.5 mg/L 2,4-D was 100%. Much greater amounts of calli could then be obtained by repeated subculture on MS medium supplemented with 3.0 mg/L 6-BA and 1.0 mg/L KT. Furthermore, transgenic calli expressing the FtCHS1 gene were obtained viaAgrobacterium-mediatedtransformation. Overexpressing FtCHS1 in tartary buckwheat callus led tothe marked promotion of flavonol (P<0.01) and anthocyanin accumulation (P<0.05) due to the dramatic upregulation of the transcription of FtCHI, FtCHS2, FtFLS1, FtFLS2, FtFLS3 and FtDFR1, the genes of key enzymes involved in the flavonol and anthocyanin biosynthesis pathways (P < 0.01). This study provides solid support for further transgenic manipulation of calli as part of a system for regenerating tartary buckwheat.

A key metabolic gene for recurrent freshwater colonization and radiation in fishes

Colonization of new ecological niches has triggered large adaptive radiations. Although some lineages have made use of such opportunities, not all do so. The factors causing this variation among lineages are largely unknown. Here, we show that deficiency in docosahexaenoic acid (DHA), an essential ω-3 fatty acid, can constrain freshwater colonization by marine fishes. Our genomic analyses revealed multiple independent duplications of the fatty acid desaturase gene Fads2 in stickleback lineages that subsequently colonized and radiated in freshwater habitats, but not in close relatives that failed to colonize. Transgenic manipulation of Fads2 in marine stickleback increased their ability to synthesize DHA and survive on DHA-deficient diets. Multiple freshwater ray-finned fishes also show a convergent increase in Fads2 copies, indicating its key role in freshwater colonization.

GUY1 confers complete female lethality and is a strong candidate for a male-determining factor in Anopheles stephensi

Despite their importance in sexual differentiation and reproduction, Y chromosome genes are rarely described because they reside in repeat-rich regions that are difficult to study. Here, we show that Guy1, a unique Y chromosome gene of a major urban malaria mosquito Anopheles stephensi, confers 100% female lethality when placed on the autosomes. We show that the small GUY1 protein (56 amino acids in length) causes female lethality and that males carrying the transgene are reproductively more competitive than their non-transgenic siblings under laboratory conditions. The GUY1 protein is a primary signal from the Y chromosome that affects embryonic development in a sex-specific manner. Our results have demonstrated, for the first time in mosquitoes, the feasibility of stable transgenic manipulation of sex ratios using an endogenous gene from the male-determining chromosome. These results provide insights into the elusive M factor and suggest exciting opportunities to reduce mosquito populations and disease transmission.