Plant innate immunity relies on successful detection of microbe-associated molecular patterns (MAMPs) of invading microbes via pattern recognition receptors (PRRs) at the plant cell surface. Here, we report two homologous rice (Oryza sativa) lysin motif–containing proteins, LYP4 and LYP6, as dual functional PRRs sensing bacterial peptidoglycan (PGN) and fungal chitin. Live cell imaging and microsomal fractionation consistently revealed the plasma membrane localization of these proteins in rice cells. Transcription of these two genes could be induced rapidly upon exposure to bacterial pathogens or diverse MAMPs. Both proteins selectively bound PGN and chitin but not lipopolysaccharide (LPS) in vitro. Accordingly, silencing of either LYP specifically impaired PGN- or chitin- but not LPS-induced defense responses in rice, including reactive oxygen species generation, defense gene activation, and callose deposition, leading to compromised resistance against bacterial pathogen Xanthomonas oryzae and fungal pathogen Magnaporthe oryzae. Interestingly, pretreatment with excess PGN dramatically attenuated the alkalinization response of rice cells to chitin but not to flagellin; vice versa, pretreatment with chitin attenuated the response to PGN, suggesting that PGN and chitin engage overlapping perception components in rice. Collectively, our data support the notion that LYP4 and LYP6 are promiscuous PRRs for PGN and chitin in rice innate immunity.

Selenium (Se) is essential for human health, however, Se is deficient in soil in many places all around the world, resulting in human diseases, such as notorious Keshan disease and Keshin–Beck disease. Therefore, Se biofortification is a popular approach to improve Se uptake and maintain human health. Beneficial microorganisms, including mycorrhizal and root endophytic fungi, dark septate fungi, and plant growth-promoting rhizobacteria (PGPRs), show multiple functions, especially increased plant nutrition uptake, growth and yield, and resistance to abiotic stresses. Such functions can be used for Se biofortification and increased growth and yield under drought and salt stress. The present review summarizes the use of mycorrhizal fungi and PGPRs in Se biofortification, aiming to improving their practical use.

Mildew resistance Locus O (MLO), a gene family specific to plants, plays significant roles in the resistance to powdery mildew (PM) and response to a variety of abiotic stresses, plant growth and development. Despite their importance as barley, rice, wheat, few studies are reported in dicots except Arabidopsis; no global analysis has been performed in the burgeoning model fruit plant sweet orange (Citrus sinensis). The recent release of the genome sequences of C. sinensis provides an opportunity to conduct a comprehensive overview the evolution and features of the MLO gene family in sweet orange. In this study, amount to 14 members of the Citrus sinensis MLO gene (CisMLO) family according to their gene structures, conserved motifs, and similitude among their presumptive Arabidopsis and rice orthologs were identified in silico. Based on these analyses, all CisMLOs were grouped into six clades and expanded partly due to one tandem duplication and two segmental duplication events. Survey of their chromosomal distributions uncovered that 14 CisMLOs are localized across 6 chromosomes. Multiple-sequence alignments showed that 11 of them shared seven highly conserved transmembrane domains (TMs), while all of the sweet orange MLO proteins except CisMLO4/14 had a calmodulin-binding domain for MLO function. Expression analysis demonstrated that the MLO gene family has a diverse tissue-specific expression profiles in the sweet orange development and plays potential critical roles in stress responses. These findings will facilitate further studies of evolutionary pattern and biological functions of MLO genes in sweet orange.