Genome-Wide Identification of Malectin/Malectin-Like Domain Containing Protein Family Genes in Rice and Their Expression Regulation Under Various Hormones, Abiotic Stresses, and Heavy Metal Treatments

Malectin/malectin-like domain containing proteins are a novel identified protein subfamily of lectins that regulates various functional bioprocesses in plants. However, little is known about the phylogenetic relationships and functions of this gene family in rice. Here, in this study, a total of 84 malectin/malectin-like domain containing proteins, including 67 malectin/malectin-like receptor-like kinases (MRLKs) and 17 malectin/malectin-like receptor-like proteins (MRLPs), were identified in rice. These MRLK and MRLP proteins can be classified into four subfamilies based on the malectin/malectin-like domain present in their extracellular regions. The OsMRLK and OsMRLP gene family members are localized on all the chromosomes in rice genome with the members within the same subfamily sharing similar exon-intron distribution and motif composition. The multiple members and diverse gene and protein structures demonstrate that the malectin/malectin-like domain protein family underscores a functional diversity and divergence in rice. In addition, the expression levels of the OsMRLK gene family members are greatly varied between the tissues and organs at different developmental stages of rice. Furthermore, the majority of the tested OsMRLKs showed significant upregulation in transcripts under a number of abiotic stresses, hormonal applications, and heavy metals, suggesting the vital roles of the OsMRLK genes in rice development and multi-stress tolerance. The results obtained here provide a well fundament for further clarification of the roles of the malectin/malectin-like domain containing proteins in plants.