Low temperature is the most common abiotic stress factor in peanut cultivation. Chitooligosaccharide (COS) plays an important role in the low-temperature resistance in plants, however, the role of COS in regulating the cold tolerance in peanuts is not clear. This research investigated the effects of exogenous COS on peanut seedlings in response to low temperatures. The results showed that exogenous COS can significantly alleviate the cooling symptoms of seedlings by reducing the content of malondialdehyde (MDA) and reactive oxygen species (ROS) under simulated low-temperature conditions (8 °C). These reductions may be related to the elevation of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and polyphenoloxidase (PPO) activities and the increased contents of osmotic substances such as soluble sugars (SS), soluble protein (SP), proline (Pro), and total phenols (TP) compared with those in untreated seedlings. Meanwhile, the contents of chlorophyll a and b in a peanut leaf also increased, as well as the net photosynthetic rate (Pn), resulted in an increased plant height, a heavier fresh weight, and an increased dry weight. Notably, the treatment of 100 mg·L⁻¹ COS had maximum gain effects compared with those of other treatments. In summary, this study revealed the usage of COS for chilling stress alleviation, and 100 mg L⁻¹ foliar spraying is recommended.

The gibberellic acid-stimulated Arabidopsis (GASA) gene family is essential for plant growth and development, hormone level control, and phytohormone signal transmission. Different plants have been shown to contain numerous GASA homologs. However, there is no knowledge about these proteins in peanuts. In the current study, we performed a thorough bioinformatics and expression analysis and found 20, 22, and 40 GASA genes by genome-wide analyses of A. hypogaea L., A. duranensis, and A. ipaensis, respectively. We analyzed and predicted the physical properties of these genes. Based on the results of our phylogenetic analysis, the evolutionary tree constructed from the 40 AhGASA proteins was divided into seven categories, forming a total of 14 gene pairs. According to our observations, tandem duplication is a significant factor in the expansion of the GASA gene family. AhGASA was unevenly distributed on 20 chromosomes, and 17 tandem duplicated genes were identified. A co-lineage analysis with the A/B subgenome identified 69 linear/parallel homologous gene pairs. A cis-element analysis revealed that the AhGASA protein is crucial for hormone responsiveness. In materials with different size traits at various stages of peanut pod development, transcriptomics and RT-qPCR analyses revealed that AhGASA genes are expressed at various levels and are tissue-specific. This finding suggests that some AhGASA genes may be involved in controlling peanut pod size. This study suggests that GASA genes are crucial for controlling the development of peanut pods and provides the first systematic identification and analysis of GASA genes in peanut. These findings will help future research into the function of the GASA gene in the cultivated peanut.