Genome-wide characterization of SINA E3 ubiquitin ligase family members and their expression profiles in response to various abiotic stresses and hormones in kiwifruit.

SINA (Seven in absentia) proteins in the subtype of E3 ubiquitin ligase family have important functions in regulating the growth and development as well as in response to abiotic and biotic stresses in plants. However, the characteristics and possible functions of SINA family proteins in kiwifruit are not studied. In this research, a total number of 11 AcSINA genes in the kiwifruit genome were identified. Chromosome location and multiple sequence alignment analyses indicated that they were unevenly distributed on 10 chromosomes and all contained the typical N-terminal RING domain and C-terminal SINA domain. Phylogenetic, gene structure and collinear relationship analyses revealed that they were highly conserved with the same gene structure, and have gone through segmental duplication events. Expression pattern analyses demonstrated that all AcSINAs were ubiquitously expressed in roots, stems and leaves, and were responsive to different abiotic and plant hormone treatments with overlapped but distinct expression patterns. Further yeast two-hybrid and Arabidopsis transformation analyses demonstrated most AcSINAs interacted with itself or other AcSINA members to form homo- or heterodimers, and ectopic expression of AcSINA2 in Arabidopsis led to hypersensitive growth phenotype of transgenic seedlings to ABA treatment. Our results reveal that AcSINAs take part in the response to various abiotic stresses and hormones, and provide important information for the functional elucidation of AcSINAs in vine fruit plants.

Variation of Aroma Components of Pasteurized Yogurt with Different Process Combination before and after Aging by DHS/GC-O-MS.

Pasteurized yogurt is a healthy yogurt that can be stored in ambient temperature conditions. Dynamic headspace sampling (DHS) combined with gas chromatography-olfactory mass spectrometry (GC-O-MS), sensory evaluation, electronic nose (E-nose), and partial least squares discriminant analysis (PLS-DA) were used to analyze the flavor changes of pasteurized yogurt with different process combinations before and after aging. The results of odor profiles showed that the sensory descriptors of fermented, sweet, and sour were greatly affected by different process combinations. The results of odor-active compounds and relative odor activity value (r-OAV) showed that the combination of the production process affected the overall odor profile of pasteurized yogurt, which was consistent with the sensory evaluation results. A total of 15 odor-active compounds of 38 volatile compounds were detected in pasteurized yogurt samples. r-OAV results revealed that hexanal, (E)-2-octenal, 2-heptanone, and butanoic acid may be important odor-active compounds responsible for off-odor in aged, pasteurized yogurt samples. PLS-DA and variable importance of projection (VIP) results showed that butanoic acid, hexanal, acetoin, decanoic acid, 1-pentanol, 1-nonanal, and hexanoic acid were differential compounds that distinguish pasteurized yogurt before and after aging.

Characterization of Key Odor-Active Off-Flavor Compounds in Aged Pasteurized Yogurt by Sensory-Directed Flavor Analysis.

The purpose of this study was to determine the key odor-active compounds contributing to the off-flavor of aged pasteurized yogurt (APY) using sensory-directed flavor analysis. Additionally, different extraction methods were compared to determine their effects on the volatile compounds, including dynamic headspace sampling (DHS), solid-phase microextraction, and stir bar sorptive extraction, and DHS was found to be suitable for this study. The results showed that comprehensive two-dimensional gas chromatography-olfactometry-mass spectrometry analysis (GC × GC-O-MS) had more advantages in separating and identifying the volatile compounds than the traditional GC-O-MS. A total of 17 odor-active compounds were determined in the fresh pasteurized yogurt and APY samples by DHS coupled with GC × GC-O-MS. The dynamic headspace dilution analysis demonstrated that 2-heptanone and hexanal were the most vital components in APY with the highest flavor dilution factor. Furthermore, the spiking and omission experimental results revealed that the odor-active compounds, such as 2-heptanone, butanoic acid, pentanoic acid, hexanal, and (E)-2-heptenal, were the key odor-active off-flavor contributors in APY. Therefore, these compounds could be used as potential indicators to determine the freshness of pasteurized yogurt.