The First Line of Defense: Receptor-like Protein Kinase-Mediated Stomatal Immunity

Zhe Wang,Xiaoping Gou

doi:10.3390/ijms23010343

Abstract

Stomata regulate gas and water exchange between the plant and external atmosphere, which are vital for photosynthesis and transpiration. Stomata are also the natural entrance for pathogens invading into the apoplast. Therefore, stomata play an important role in plants against pathogens. The pattern recognition receptors (PRRs) locate in guard cells to perceive pathogen/microbe-associated molecular patterns (PAMPs) and trigger a series of plant innate immune responses, including rapid closure of stomata to limit bacterial invasion, which is termed stomatal immunity. Many PRRs involved in stomatal immunity are plasma membrane-located receptor-like protein kinases (RLKs). This review focuses on the current research progress of RLK-mediated signaling pathways involved in stomatal immunity, and discusses questions that need to be addressed in future research.

Highlights

Guard cells are a kind of specialized kidney-shaped epidermal cells
It is worth pointing out that OsRLCK185 is required in rice for both reactive oxygen species (ROS) production and mitogen-activated protein kinases (MAPKs) signaling triggered by chitin, two immune responses in Arabidopsis mediated by BOTRYTISINDUCED KINASE 1 (BIK1) and PBS1-Like 27 (PBL27), respectively, which suggests that the functions of these Receptor-like cytoplasmic kinases (RLCKs) VII members are differentiated in chitin-induced stomatal closure
The importance of stomata in immune processes has long been recognized [120,121], the mechanism was not revealed until it was found that stomatal closure induced by bacteria requires FLAGELLIN-SENSING 2 (FLS2) and the guard cell-specific OST1 kinase [15]

Summary

Introduction

Guard cells are a kind of specialized kidney-shaped epidermal cells. The pore between a pair of guard cells is called a stoma, meaning mouth in Greek. Abscisic acid (ABA) regulates stomatal movement under drought conditions or bacteria invasion by inducing the production of reactive oxygen species (ROS) and a transient increase of cytosolic Ca2+ ([Ca2+]cyt) in guard cells [7,8]. Methyl jasmonate (MeJA) can activate Ca2+ permeable cation channels in guard cells to close the stomata, which is similar to the mechanism of ABA-regulated stomatal closure [11,12]. Continuous treatment with E. coli cannot re-open the stomata [15] Both plants and human bacteria can induce stomatal closure, Pst DC3000 acquired a specific mechanism during. Arabidopsis L-type lectin receptor-like protein kinase (LecRK) family contains 45 members, many of which were reported to regulate plant innate immunity by sensing various signals, such as extracellular purine molecules and PAMPs [35–37]. It is worth noting that lines of evidence suggested that these RLKs mediate signals to regulate stomatal movement during plant immunity. We discuss recent findings on stomatal immunity, mainly focusing on RLK-mediated signaling and the downstream regulators involved in this process

FLS2 Perceives Flg22 to Mediate Stomatal Immunity

CERK1-Mediated Chitin Signaling Regulates Stomatal Immunity

LecRKs Mediate Various Signals to Regulate Stomatal Immunity

Conclusions and Future Perspectives