CsFAMA

CsFAMA is a gene encoding a basic helix–loop–helix (bHLH) transcription factor identified as a FAMA-like ortholog in species designated by the Cs prefix, commonly Citrus sinensis. Based on sequence similarity to Arabidopsis thaliana FAMA, CsFAMA is predicted to encode a nuclear protein that participates in stomatal development by promoting final differentiation of guard cells and helping terminate the stomatal lineage program. As a member of the FAMA family within the larger bHLH transcription factor group, CsFAMA is expected to contain the characteristic basic DNA-binding region and dimerization helices that enable interaction with other bHLH partners.

Expression and regulation are inferred from knowledge of FAMA in model plants: FAMA is typically expressed in developing leaf epidermis during stomatal lineage progression, and its activity is coordinated with other stomatal regulators such as SPCH and MUTE. For CsFAMA, similar epidermal expression is presumed, though experimental confirmation may be limited. Regulatory relationships with upstream and downstream factors in CsCs are not yet fully established, and functional confirmation remains an area of active research.

Evolutionary context and significance: FAMA homologs are broadly conserved across land plants, and CsFAMA represents the Citrus counterpart within this conserved stomatal-regulation network. Investigating CsFAMA can provide insights into how stomatal development is controlled in citrus species and may inform breeding strategies related to gas exchange and water use efficiency. Current knowledge of CsFAMA is largely based on homology with AtFAMA; detailed functional studies in Cs species are needed to define its precise role.