Effects of TT8 and HB12 Silencing on the Relations between the Molecular Structures of Alfalfa ( Medicago sativa) Plants and Their Nutritional Profiles and In Vitro Gas Production

Effect of Anaerobic Calcium Oxide Alkalization on the Carbohydrate Molecular Structures, Chemical Profiles, and Ruminal Degradability of Rape Straw

To improve the utilization efficiency of rape straw, anaerobic calcium oxide (CaO) alkalization was conducted, and advanced molecular spectroscopy was applied, to detect the internal molecular structural changes. Rape straw was treated with different combinations of CaO (3%, 5%, and 7%) and moisture levels (50% and 60%) and stored under anaerobic conditions. We investigated the carbohydrate chemical constituents, the ruminal neutral detergent fiber (aNDF) and acid detergent fiber (ADF) degradation kinetics, and the carbohydrate molecular structural features. CaO-treated groups were higher (p < 0.05) for ash, Ca, non-fiber carbohydrate, soluble fiber, and the ruminal degradability of aNDF and ADF. In contrast, they were lower (p < 0.05) for the contents of aNDF, ADF, and indigestible fiber. With CaO levels rising from 3% to 7%, the content of aNDF and ADF linearly decreased (p < 0.05). CaO treatment and anaerobic storage changed the molecular characteristics, including structural parameters related to total carbohydrates (TC), cellulosic compounds (CEC), and structural carbohydrates (STC). Alterations in cellulosic compounds' spectral regions were highly correlated with the differences in carbohydrate chemical constituents and the ruminal digestibility of rape straw. In summary, CaO treatment and anaerobic storage altered the molecular structural parameters of carbohydrates, leading to an enhancement in the effective degradability (ED) of aNDF and ADF in rape straw. From the perspective of processing cost and effectiveness, 5% CaO + 60% moisture could be suggested as a recommended treatment combination.

Overexpression of miR156 and Silencing SPL6RNAi and SPL13RNAi Genes in Medicago sativa on the Changes of Carbohydrate Physiochemical, Fermentation, and Nutritional Profiles

This study aimed to explore the comparative effects of overexpressing miR156 with individually silencing SPL6RNAi and SPL13RNAi genes on carbohydrate physiochemical, fermentation, and nutritional profiles of alfalfa (Medicago sativa). Three sub-genotypes of miR156 overexpressed (miR156 OE), SPL6RNAi, and SPL13RNAi grown with the wild type (WT) in a greenhouse were harvested 3 times at an early vegetative stage. Samples were freeze-dried, ground, and analyzed for carbohydrate nutritional profiles in terms of chemical composition, CNCPS fractions, energetic values, in vitro degradation, and fermentation characteristics. Results showed that miR156 OE had lower fiber and higher energy compared to all other genotypes. Moreover, miR156 OE had higher starch compared to SPL13RNAi and higher DM degradation compared to WT and SPL13RNAi. In conclusion, overexpression of miR156 decreased the fiber content of alfalfa but increased energy and DM degradation. SPL6RNAi was more similar to miR156 OE alfalfa in chemical composition and degradation, indicating that the SPL6RNAi gene plays an important role in the miR156 overexpression event.

Using advanced vibrational molecular spectroscopy (ATR-Ft/IRS) to study heating process induced changes on protein molecular structure of biodegradation residues in cool-climate adapted faba bean seeds: Relationship with rumen and intestinal protein digestion in ruminant systems

The objective of this study was to evaluate the effects of heating process on protein molecular structure from ruminal degradation residues in cool-climate adapted faba bean seeds in relation to crude protein (CP), in situ degradation kinetics, rumen protein degradation and intestinal protein digestion parameters in dairy cows. Seeds of six faba bean varieties with low (Snowbird, Snowdrop, 219_16) and normal tannin (Fatima, 346_10, SSNS_1) were collected from three different locations, and were heated 3 min by microwave irradiation (MI, dry heating) or heated 1 h by steam pressure toasting (SP, moist heating) or kept raw as a control. Heat treated samples were used for rumen incubating 24, 12, 8, 4, 2, 0 h(s) in two replicate runs and then residues from 12 h of rumen degradation were used for three steps in vitro technique for determining intestinal protein digestion. Attenuated total reflectance Fourier transforms infrared spectroscopy (ATR-Ft/IRS) was used for analyzing protien molecular structure of residual faba bean seeds. The results showed that SP increased the intensities of amide I, amide II, α-helix and β-sheet but decreased amide I to amide II height and area ratio, α-helix to β-sheet height ratio from 12 and 24 h of ruminal degradation, and MI decreased all the intensities of amide I, amide II, α-helix and β-sheet and ratios except amide I to amide II area ratio of residues from 24 h of ruminal degradation. Additionally, the intensities of amide I, amide II, α-helix and β-sheet had a unique pattern of increasing first and then decreasing with the increasing ruminal digestion time for SP treatment, while amide I to amide II height and area ratio, α-helix to β-sheet height ratio were declining. For the MI groups, this pattern was not observed and the intensities were rather consistent across the digestion process. Rumen protein degradation parameters including rumen bypass crude protein (BCP) or rumen undegradable protein (RUP) and rumen degradable protein (RDP) closely correlated with protein molecular structure of to peak heights, areas and ratios. Regression equations based on residual protein molecular structure presented a good estimation power for soluble fraction (S, R² = 0.79), degradable fraction (D, R² = 0.805), BCP (R² = 0.941), RUP (R² = 0.941) and RDP (R² = 0.811). Overall, heat-induced changes in rumen residual protein molecular structures were related to CP, in situ degradation kinetics, rumen protein degradation and rumen protein digestion parameters.

Biohydrogen production through active saccharification and photo-fermentation from alfalfa

Studying biohydrogen production from alfalfa is of practical significance to cleaner production and biomass utilization. The performances of biohydrogen production through active/passive saccharification and photo-fermentation were compared. The effects of initial pH, substrate concentration, and cellulase loading on biohydrogen production from alfalfa by photosynthetic bacteria HAU-M1 were presented. It was found that the maximum hydrogen yield of 55.81 mL/g was achieved at initial pH of 6.90, substrate concentration of 31.23 g/mL, and cellulase loading of 0.13 g/g. Hydrogen yield of active saccharification and photo-fermentation was much higher as compare to passive saccharification and photo-fermentation. Initial pH value showed a more significant influence on photosynthetic bacteria in comparison to cellulase in active saccharification and photo-fermentation biohydrogen production. The low yield of propionic acid suggested that it was an efficient photosynthetic hydrogen production. Photo-fermentation hydrogen production from alfalfa provides a novel path for efficient utilization of alfalfa.

Effects of silencing TT8 and HB12 on in vitro nutrients degradation and VFA production in relation to molecular structures of alfalfa (Medicago sativa)

BACKGROUND

Transparent Testa8 (TT8) and Homeobox12 (HB12) are two transcriptional factors in plant phenylpropanoid pathways and were reported to be positively related to lignin content. Alfalfa with silenced TT8 (TT8i) and HB12 (HB12i) was therefore generated using the RNA interference (RNAi) technique. Although lignin was found to be high in HB12i, such gene-silencing of alfalfa resulted in nutrient profiles that might be suitable for grazing. To extend the nutritional evaluation of transformed alfalfa, ground samples of 11 HB12i, 5 TT8i and 4 wild type (WT) were incubated in rumen fluid : buffer solution for 0, 2, 4, 8, 12, 24 and 48 h at 39 °C. Dry matter (DM) and neutral detergent fiber (NDF) degradations at each time point, and production of volatile fatty acids (VFA) at 4, 12, 24 and 48 h were analyzed, as well as degradation and production kinetics. The correlations and regressions between nutritive profiles and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectral parameters were determined.

RESULTS

Both transformed genotypes had lower DM degradation and HB12i had lower VFA production compared with WT. Structural carbohydrate (STC) parameters were found to be negatively correlated with DM degradation and VFA production. The kinetics of DM degradation and VFA production were predicted from spectral parameters with good estimation power.

CONCLUSION

Silencing of HB12 and TT8 affected fermentation characteristics of alfalfa and some fermentation characteristics were predictable from spectral parameters using ATR-FTIR spectroscopy. © 2019 Society of Chemical Industry.

Silencing TT8 and HB12 Decreased Protein Degradation and Digestion, Microbial Synthesis, and Metabolic Protein in Relation to Molecular Structures of Alfalfa (Medicago sativa)

This study aimed to explore the effects of silencing HB12 and TT8 genes on protein utilization characteristics of alfalfa. Ground samples of 11 HB12-silenced (HB12i), 5 TT8-silenced (TT8i) and 4 wild type (WT) were incubated in a Daisy II incubator with N¹⁵ labeled ammonium sulfate for 0, 4, 8, 12, and 24 h. CP degradation and degradational kinetics, microbial nitrogen fractions, and protein metabolic profiles were determined. Moreover, relationships between protein profiles and FTIR spectral parameters were estimated. Results showed that transgenic alfalfa had lower CP degradation, microbial protein, and total available protein compared with WT, especially for HB12i. In addition, CP degradation and protein metabolic profiles were closely correlated with FTIR spectral parameters and thereby could be predicted from spectral parameters. In conclusion, silencing of HB12 and TT8 genes in alfalfa decreased protein degradational and metabolic profiles, which were predictable with FTIR spectral parameters.

Biodegradation Profiles of Proanthocyanidin-Accumulating Alfalfa Plants Coexpressing Lc- bHLH and C1-MYB Transcriptive Flavanoid Regulatory Genes

The utilization of the nutrient potential of alfalfa ( Medicago sativa L.) cannot be maximized because of its rapidly degradable protein content in the rumen, leading to waste and various digestive disorders. This might be alleviated if protein-binding proanthocyanidins are present in aerial parts of alfalfa forage in adequate amounts. The Lc (bHLH) and C1 (MYB) genes of maize are transcription factors known to be collectively involved in the regulation of anthocyanin biosynthetic pathways. The objective of this study was to investigate the effect of Lc and C1 gene transformations on the proanthocyanidin content, nutrient composition, and degradation characteristics of proteins and carbohydrates by comparing the transgenic alfalfa with its parental nontransgenic (NT) alfalfa and commercial AC-Grazeland cultivar. The DNA extracted from transgenic plants was tested for the presence of respective transgenes by amplification with specific primers of respective transgenes using PCR. Both Lc-single and LcC1-double transgenic alfalfa accumulated both monomeric and polymeric proanthocyanidins with total proanthocyanidins ranging from ca. 460 to 770 μg/g of DM. The C1-transgenic alfalfa did not accumulate proanthocyanidins similar to NT alfalfa. The C1 gene increased the NPN content significantly only in C1-single and Lc1C1-double transgenic alfalfa. The LcC1 combination seemed to have a synergic effect on reducing sugar in alfalfa. In contrast, the Lc gene appears to have a negative effect on starch content. The C1 gene tended to lower the PB3 content irrespective of the presence of the Lc gene. Although the cotransformation of Lc and C1 increased the total N/CHO ratio compared to Lc single gene transformation, the total N/CHO ratio of transgenic alfalfa was not significantly different from NT. In conclusion, Lc-bHLH single and LcC1 double gene transformation resulted in the accumulation of proanthocyanidins and affected the chemical profiles in alfalfa, which altered ruminal degradation patterns and impacted the nutrient availability of alfalfa in ruminant livestock systems.