"Single-pole dual-control" competing mode in plants.

Plant development and pattern formation depend on diffusible signals and location cues. These developmental signals and cues activate intracellular downstream components through cell surface receptors that direct cells to adopt specific fates for optimal function and establish biological fitness. There may be a single-pole dual-control competing mode in controlling plant development and microbial infection. In plant development, paracrine signaling molecules compete with autocrine signaling molecules to bind receptors or receptor complexes, turn on antagonistic molecular mechanisms, and precisely regulate developmental processes. In the process of microbial infection, two different signaling molecules, competing receptors or receptor complexes, form their respective signaling complexes, trigger opposite signaling pathways, establish symbiosis or immunity, and achieve biological adaptation. We reviewed several "single-pole dual-control" competing modes, focusing on analyzing the competitive commonality and characterization of "single-pole dual-control" molecular mechanisms. We suggest it might be an economical protective mechanism for plants' sequentially and iteratively programmed developmental events. This mechanism may also be a paradigm for reducing internal friction in the struggle and coexistence with microbes. It provides extraordinary insights into molecular recognition, cell-to-cell communication, and protein-protein interactions. A detailed understanding of the "single-pole dual-control" competing mode will contribute to the discovery of more receptors or antagonistic peptides, and lay the foundation for food, biofuel production, and crop improvement.

Peptides/receptors signaling during plant fertilization.

Double fertilization is a unique and particularly complicated process for the generation alternation of angiosperms. Sperm cells of angiosperms lose the motility compared with that of gymnosperms. The sperm cells are passively carried and transported by the pollen tube for a long journey before targeting the ovule. Two sperm cells are released at the cleft between the egg and the central cell and fused with two female gametes to produce a zygote and endosperm, respectively, to accomplish the so-called double fertilization process. In this process, extensive communication and interaction occur between the male (pollen or pollen tube) and the female (ovule). It is suggested that small peptides and receptor kinases play critical roles in orchestrating this cell-cell communication. Here, we illuminate the understanding of phases in the process, such as pollen-stigma recognition, the hydration and germination of pollen grains, the growth, guidance, and rupture of tubes, the release of sperm cells, and the fusion of gametes, by reviewing increasing data recently. The roles of peptides and receptor kinases in signaling mechanisms underlying cell-cell communication were focused on, and directions of future studies were perspected in this review.

Receptors in the Induction of the Plant Innate Immunity.

Plants adjust amplitude and duration of immune responses via different strategies to maintain growth, development, and resistance to pathogens. Pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI) play vital roles. Pattern recognition receptors, comprising a large number of receptor-like protein kinases and receptor-like proteins, recognize related ligands and trigger immunity. PTI is the first layer of the innate immune system, and it recognizes PAMPs at the plasma membrane to prevent infection. However, pathogens exploit effector proteins to bypass or directly inhibit the PTI immune pathway. Consistently, plants have evolved intracellular nucleotide-binding domain and leucine-rich repeat-containing proteins to detect pathogenic effectors and trigger a hypersensitive response to activate ETI. PTI and ETI work together to protect plants from infection by viruses and other pathogens. Diverse receptors and the corresponding ligands, especially several pairs of well-studied receptors and ligands in PTI immunity, are reviewed to illustrate the dynamic process of PTI response here.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

The Arabidopsis Receptor Kinase ZAR1 Is Required for Zygote Asymmetric Division and Its Daughter Cell Fate.

Asymmetric division of zygote is critical for pattern formation during early embryogenesis in plants and animals. It requires integration of the intrinsic and extrinsic cues prior to and/or after fertilization. How these cues are translated into developmental signals is poorly understood. Here through genetic screen for mutations affecting early embryogenesis, we identified an Arabidopsis mutant, zygotic arrest 1 (zar1), in which zygote asymmetric division and the cell fate of its daughter cells were impaired. ZAR1 encodes a member of the RLK/Pelle kinase family. We demonstrated that ZAR1 physically interacts with Calmodulin and the heterotrimeric G protein Gß, and ZAR1 kinase is activated by their binding as well. ZAR1 is specifically expressed micropylarly in the embryo sac at eight-nucleate stage and then in central cell, egg cell and synergids in the mature embryo sac. After fertilization, ZAR1 is accumulated in zygote and endosperm. The disruption of ZAR1 and AGB1 results in short basal cell and an apical cell with basal cell fate. These data suggest that ZAR1 functions as a membrane integrator for extrinsic cues, Ca2+ signal and G protein signaling to regulate the division of zygote and the cell fate of its daughter cells in Arabidopsis.