Final answer:
The statement about the role of brassinosteroids in plants is true. They act similarly to steroid hormones in animals by binding to receptors that regulate gene expression through DNA binding, and their interaction with auxin is pivotal in plant growth and development.
Step-by-step explanation:
The statement that plants synthesize a class of steroids called brassinosteroids that function by binding to nuclear steroid hormone receptors, which in turn bind to DNA regulatory regions to control the activity of specific genes, is True. Brassinosteroids are indeed a class of plant hormones that regulate various physiological processes by binding to specific receptors, which then modulate the expression of target genes.
Like steroid hormones in animals, brassinosteroids cross cell membranes and bind to receptor proteins. This hormone-receptor complex can either be located in the cytoplasm or directly in the nucleus. Upon binding, the complex migrates to the DNA and binds to specific regulatory elements, which are parts of the promoters of target genes. This interaction plays a crucial role in the transcription regulation of those genes, either enhancing or repressing their activity.