Genome-Wide Identification of the bHLH Gene Family in Magnolia sieboldii and Response of MsPIFs to Different Light Qualities

The basic helix-loop-helix (<i>bHLH</i>) gene family has been identified in many species. However, the characteristics and functions in the <i>Magnolia sieboldii</i> K. Koch (<i>M. sieboldii</i>), which is located in one of the original groups of angiosperms, are still unclear. Here, a total of 142 <i>MsbHLH</i> members were identified and divided into 27 subfamilies. MsbHLH proteins are relatively conserved during evolution. Collinearity analysis illustrated that the expansion of the <i>MsbHLH</i> gene family primarily occurred through segmental duplication. All members contain light-responsive elements in their promoters. Different light quality treatments were carried out to simulate the light environment in the forest after seed abscission. It was found that the expression levels of <i>MsPIF1</i>, <i>MsPIF3b</i>, <i>MsPIF4</i>, and <i>MsPIF7</i> gradually increased under far-red light and inhibited seed germination. Overall, this study lays the foundation for further exploration of the response mechanism of <i>MsPIFs</i> to seed germination under different light qualities. It will provide a reference for the germination of morphophysiological dormant seeds like those of <i>M. sieboldii</i> under light conditions.