LbMYB368 from the recretohalophyte Limonium bicolor promotes salt gland development and salinity tolerance

Halophytes can grow and reproduce normally in an environment containing more than 200 mM NaCl, offering untapped gene resources for improving crop salinity tolerance. As a recretohalophyte, Limonium bicolor can secrete excess Na⁺ through salt glands, specialized structures on the leaf and stem epidermis. Here, we identified a MYB transcription factor gene, LbMYB368, that is highly expressed during salt gland development. We confirmed its expression in salt glands using RNA in situ hybridization and a promoter reporter construct. To investigate in detail the roles of LbMYB368 in salinity tolerance, we overexpressed and knocked down the gene, via virus-induced gene silencing (VIGS), in L. bicolor. The transgenic L. bicolor overexpression lines developed more salt glands, while the VIGS plants had fewer salt glands. The salt secretion ability and salt tolerance of these plants were correlated with the changes in salt gland development, indicating that LbMYB368 plays an important role in the salt tolerance of L. bicolor by enhancing salt gland development and salt secretion. We also investigated the effect of LbMYB368 on enhanced salinity tolerance when heterologously expressed in Arabidopsis to assess its potential applications in non-halophytes for future conferring salinity tolerance in crops.