Expression dosage effects of a small number of genes after the artificial doubling of weeping forsythia

Whole genome doubling (WGD) plays a critical role in plant evolution, yet the mechanisms underlying the maintenance of overall equilibrium following an artificial doubling event, as well as its impact on phenotype and adaptability, remain unclear. By comparing the gene expression of naturally occurring weeping forsythia diploids and colchicine-induced autotetraploids under normal growth conditions and cold stress, we identified gene expression dosage responses resulting from ploidy change. Only a small proportion of effectively expressed genes showed dosage effect, and most genes did not exhibit significant expression differences. However, the genes that showed expression dosage effect were largely random. The autotetraploids had slower overall growth rates, possibly resulting from negative gene dosage effects on zeatin synthesis and multiple metabolic delays caused by other negative dosage genes. Our comparative analysis of cold response genes in diploids and autotetraploids revealed that genes related to "response to abscisic acid" and "cold acclimation" were key factors contributing to greater cold tolerance in the autotetraploids. In particular, gene expression related to "cold acclimation" might mitigate the effects of cold stress. Taken together, our findings suggested that overall gene expression equilib-rium following WGD of weeping forsythia autotetraploids was achieved through the inactivation of the majority of duplicated genes. Our research provides new insights into the mechanisms regulating expression dosage balance following polyploidization events.