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 degrees 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. (c) 2019 Society of Chemical Industry