The desire for foods with lower glycemic indices has led to the exploration of functional ingredients and novel food processing techniques. The glycemic index (GI) is a well-recognized tool to assess the capacity of foods to raise blood glucose levels. Among cereal crops, oats have shown the greatest promise for mitigating glycemic response. This review evaluated decades of research on the effects of oat components on the GI level of oat-based foods with specific emphasis on oat starch, β-glucans, proteins, and phenolics. The effects of commonly used processing techniques in oats on GI level, including heating, cooling, and germination were also discussed. In addition, the GI of oat-based foods in various physical formats such as whole grain, flakes, and flour was systematically summarized. The aim of this review was to synthesize knowledge of the field and to provide a deeper understanding of how the chemical composition and processing of oats affect GI, thereby further benefiting the development of low-GI oat foods.

Proper flowering is essential for the reproduction of all kinds of plants. Oat is an important cereal and forage crop; however, its cultivation is limited because it is a long-day plant. The molecular mechanism by which oats respond to different photoperiods is still unclear. In this study, oat plants were treated under long-day and short-day photoperiods for 10 days, 15 days, 20 days, 25 days, 30 days, 40 days and 50 days, respectively. Under the long-day treatment, oats entered the reproductive stage, while oats remained vegetative under the short-day treatment. Forty-two samples were subjected to RNA-Seq to compare the gene expression patterns of oat under long- and short-day photoperiods. A total of 634-5,974 differentially expressed genes (DEGs) were identified for each time point, while the floral organ primordium differentiation stage showed the largest number of DEGs, and the spikelet differentiation stage showed the smallest number. Gene Ontology (GO) analysis showed that the plant hormone signaling transduction and hormone metabolism processes significantly changed in the photoperiod regulation of flowering time in oat. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Mapman analysis revealed that the DEGs were mainly concentrated in the circadian rhythm, protein antenna pathways and sucrose metabolism process. Additionally, transcription factors (TFs) involved in various flowering pathways were explored. Combining all this information, we established a molecular model of oat flowering induced by a long-day photoperiod. Taken together, the long-day photoperiod has a large effect at both the morphological and transcriptomic levels, and these responses ultimately promote flowering in oat. Our findings expand the understanding of oat as a long-day plant, and the explored genes could be used in molecular breeding to help break its cultivation limitations in the future.

Insensitivity to day length is an essential trait for oat cultivation and its geographical spread to a wide range of latitudes. Daylength-insensitive oat cultivars can flower normally from low to high latitudes and may be especially well suited for a double-cropping system. However, few studies have investigated the regulatory mechanisms involved in flowering in photoperiod-insensitive oats. In this study, we compared the developmental stages of shoot apical meristems (SAMs) and transcriptome profiles between the photoperiod-insensitive oat cultivar VAO-8 and the photoperiod-sensitive oat cultivar Baiyan 2 at four time points under a short-day photoperiod. The development of Baiyan 2 was affected by short-day length, and SAMs persisted in the vegetative stage. VAO-8 responded less to photoperiod and matured normally under a short-day photoperiod. Comparative transcriptome data of the two cultivars revealed a total of 824, 1,189, 646 and 1,145 differentially expressed genes (DEGs) between VAO-8 and Baiyan 2 at four time points. Functional enrichment analysis revealed that metabolic processes related to chlorophyll biosynthesis, photosynthesis, carbohydrate metabolism and the secondary metabolism were significantly enhanced in VAO-8 compared with those in Baiyan 2. The upregulated genes involved in these processes may contribute to the flowering of VAO-8 under a short-day photoperiod. Furthermore, the differential expression of 93 transcription factor genes involved in multiple flowering pathways was observed, and these genes may play important roles in the regulation of VAO-8 flowering. The results provide a comprehensive understanding of the photoperiod-insensitive molecular mechanism of oats at the transcriptional level under a short-day photoperiod, which lay a foundation for breeding photoperiod-insensitive oat cultivars.

The MADS-box gene family is a large family of transcription factors, and its members are widely distributed in the plant kingdom. Members of this family are well known to be crucial regulators of many biological processes and environmental responses. In this study, bioinformatics methods were employed to analyze the MADS-box gene family members in the common oat, focusing on their phylogenetic relationships, gene structures, conserved motifs, evolutionary relationships, promoter analysis and responses to photoperiod and abiotic stress. A total of 175 MADS-box genes were detected in Avena sativa, which were categorized into Type I and Type II. Type II members exhibited more complex gene structures, while each subfamily showed similar gene structures and motifs. Evolutionary analysis identified 138 segmental duplication events and revealed strong syntenic conservation with Triticum aestivum (337 collinear gene pairs). Four categories of cis-elements were detected in the promoter regions of the AsMADS-box genes. qRT-PCR analysis revealed that the expression of six Type II AsMADS-box genes varied in response to ABA, GA, drought and salt. Furthermore, 23 AsMADS-box members were potentially associated with heading date when the common oat plants were exposed to different photoperiod conditions. The overexpression of chr4D_AsMADS95 in Arabidopsis thaliana led to early flowering under long-day and short-day photoperiod conditions, likely associated with a significant increase in the expression levels of flowering-related genes in transgenic plants. These findings will provide useful information for future studies on stress responses and increase our understanding of the network that regulates flowering in the common oat.