Analysis of β-aminobutyric acid enhancing cold resistance of rice seedlings based on physiological responses and transcriptome analysis

<bold>Objective</bold> Early rice seedlings are prone to low-temperature stress.This study explores the regulation of the physiological characteristics and molecular mechanisms of rice seedlings under low-temperature stress by the broad-spectrum chemical inducer β-aminobutyric acid（BABA）. <bold>Method</bold> Two-day-old rice seedlings at the panicle differentiation stage 11 were treated with 0.04-1 mmol/L BABA via root irrigation，with water treatment as the control（CK）.The seedlings were subjected to cold stress（8 ℃）for 7 days，and the seedling growth was assessed after 7 days of recovery at normal temperature.Changes in antioxidant-related enzyme activities and resistance-related substance contents from 0 to 6 days of cold stress were measured，and transcriptome sequencing was performed. <bold>Result</bold> Compared with CK，0.2 mmol/L BABA can significantly promote the recovery growth of rice seedlings after cold damage，increase the activities of SOD，CAT，APX，GR，and DHAR one day after cold stress，reduce the contents of H₂O₂，MDA，and Pro，and increase the contents of AsA and GSH.Comparing the transcriptomes of BABA treatment and CK under cold stress for 6 hours，3 days，and 6 days，a total of 2 616 differentially expressed genes were identified，of which 1 053 genes were upregulated and 1 563 genes were downregulated.GO biological process analysis showed that the differentially expressed genes were enriched in stress response，diterpenoid biosynthesis，carbohydrate metabolism，oxidative stress response，and other categories.KEGG pathway analysis revealed that the differentially expressed genes were significantly enriched in secondary metabolite biosynthesis，phenylpropanoid biosynthesis，plant hormone signal transduction，and MAPK pathways.Further analysis of hormone-related differentially expressed genes showed that under cold stress，BABA can transcriptionally activate ABA signaling while inhibiting JA and SA signaling. <bold>Conclusion</bold> BABA can enhance the antioxidant capacity of seedlings under cold stress，and regulate the expression of genes related to stress response，hormone signaling，and secondary metabolite synthesis pathways，thereby improving the cold tolerance of rice seedlings.