Research Progress on the Molecular Function of Plant-Specific LBD Gene

The LATERAL ORGAN BOUNDARIES DOMAIN(LBD) gene family, which was firstly discovered in Arabidopsis thaliana, encodes a conserved higher plant-specific LATERAL ORGAN BOUNDARIES(LOB) domain-containing protein. LBD gene is expressed in a band of cells between lateral organs and the shoot apical meristem(SAM) or at the adaxial base of lateral organs formed from the SAM. The LBD genes show a variety of tissue-specific expression patterns, suggesting that they may function in diverse developmental processes. LBD protein doesn't contain other recognizable functional motifs except for the LOB domain. Up to now, 43 members of the LBD gene family have been identified in Arabidopsis, whereas in rice(Oryza sativa) and maize(Zea mays), there are 35 and 43 LBD genes respectively. LBD genes contain two major classes which are characterized by the presence(class I) or absence(class II) of functional leucine-zipper-like motifs. In this review, we described the structure of LBD proteins, and functions of them on plant development are discussed. At the same time, the relationships among LBD genes, and those between LBD genes, plant hormones and miRNA were clarified systematically.