Physiological Responses to Chilling Stress and Transcriptome-Assisted Genome-Wide Characterization of the DREB Gene Family in Durian.

Durian is highly sensitive to chilling temperatures, which restrict its cultivation beyond tropical regions. In this study, one-year-old seedlings of the cultivars 'Musang King' and 'Monthong' were exposed to 10 °C for 7 days to characterize their phenotypic, physiological, and transcriptional responses. Leaf phenotype, membrane injury, osmotic adjustment, photosynthetic pigment contents, amylase activity, and antioxidant enzyme activities were evaluated, and transcriptome sequencing was performed using samples collected before chilling treatment and after 1 and 5 days of exposure. 'Monthong' exhibited earlier and visually more extensive leaf abscission than 'Musang King', while the two cultivars showed contrasting temporal patterns of malondialdehyde accumulation and antioxidant enzyme activities. Comparative transcriptome analysis was subsequently used to construct a Musang King-focused discovery set comprising genes prioritized based on progressive induction patterns and higher transcript abundance in 'Musang King'. Because AP2/ERF transcription factors were represented in this discovery set, the DREB gene family was characterized at the whole-genome level. A total of 81 DzDREB genes were identified and classified into six subgroups. Integration of transcriptomic response patterns, stress-related functional annotations, and promoter cis-regulatory elements supported the prioritization of a ten-gene DzDREB panel for further investigation. Exploratory seasonal field-expression profiling provided additional support for seven candidates, among which DzDREB36, DzDREB45, DzDREB62, and DzDREB66 showed comparatively stronger support across datasets. These results provide candidate resources for further functional investigation of differential chilling responses in durian.