Plasma Membrane Ca2+ Permeable Mechanosensitive Channel OsDMT1 Is Involved in Regulation of Plant Architecture and Ion Homeostasis in Rice

MID1-COMPLEMENTING ACTIVITY regulates cell proliferation and development via Ca2+ signaling in Marchantia polymorpha

MID1-COMPLEMENTING ACTIVITY (MCA) is a land plant-specific, plasma membrane protein, and Ca2+ signaling component that responds to exogenous mechanical stimuli, such as touch, gravity, and hypotonic-osmotic stress, in various plant species. MCA is essential for cell proliferation and differentiation during growth and development in rice (Oryza sativa) and maize (Zea mays). However, the mechanism by which MCA mediates cell proliferation and differentiation via Ca2+ signaling remains unknown. Here, we address this question using the liverwort Marchantia polymorpha. We show that the M. polymorpha MCA ortholog, MpMCA, is highly expressed in actively dividing regions, such as apical notches in the thalli and developing gametangiophores, and that MpMCA is a plasma membrane protein. In vivo, Ca2+ imaging using a Ca2+ sensor (yellow cameleon) revealed that MpMCA is required for maintaining proper [Ca2+]cyt levels in the apical notch region, egg cells, and antheridium cells. Mpmca mutant plants showed severe cell proliferation and differentiation defects in the thalli, gametangiophores, and gametangia, resulting in abnormal development and unsuccessful fertilization. Furthermore, expression of the Arabidopsis MCA1 gene complemented most of the defects in the growth and development of the Mpmca mutant plants. Our findings indicate that MpMCA is an evolutionarily conserved Ca2+-signaling component that regulates cell proliferation and development across the life cycle of land plants.

Evidence for the role of sound on the growth and signal response in duckweed

Sound vibration, an external mechanical force, has been proven to modulate plant growth and development like rain, wind, and vibration. However, the role of sound on plants, especially on signal response, has been usually neglected in research. Herein, we investigated the growth state, gene expression, and signal response in duckweed treated with soft music. The protein content in duckweed after music treatment for 7 days was about 1.6 times that in duckweed without music treatment. Additionally, the potential maximum photochemical efficiency of photosystem II (Fv/Fm) ratio in duckweed treated with music was 0.78, which was significantly higher in comparison with the control group (P < .01). Interestingly, music promoted the Glu and Ca signaling response. To further explore the global molecular mechanism, we performed transcriptome analysis and the library preparations were sequenced on an Illumina Hiseq platform. A total of 1296 differentially expressed genes (DEGs) were found for all these investigated genes in duckweed treated with music compared to the control group. Among these, up-regulation of the expression of metabolism-related genes related to glycolysis, cell wall biosynthesis, oxidative phosphorylation, and pentose phosphate pathways were found. Overall, these results provided a molecular basis to music-triggered signal response, transcriptomic, and growth changes in duckweed, which also highlighted the potential of music as an environmentally friendly stimulus to promote improved protein production in duckweed.

Mechanotransduction in the spotlight of mechano-sensitive channels

The study of mechanosensitive channels (MS) in living organisms has progressed considerably over the past two decades. The understanding of their roles in mechanosensation and mechanotransduction was consecrated by the awarding of the Nobel Prize in 2021 to A. Patapoutian for his discoveries on the role of MS channels in mechanoperception in humans. In this review, we first summarize the fundamental properties of MS channels and their mode of operation. Then in a second step, we provide an update on the knowledge on the families of MS channels identified in plants and the roles and functions that have been attributed to them.

The Role of Membrane Transporters in Plant Growth and Development, and Abiotic Stress Tolerance

The proteins of membrane transporters (MTs) are embedded within membrane-bounded organelles and are the prime targets for improvements in the efficiency of water and nutrient transportation. Their function is to maintain cellular homeostasis by controlling ionic movements across cellular channels from roots to upper plant parts, xylem loading and remobilization of sugar molecules from photosynthesis tissues in the leaf (source) to roots, stem and seeds (sink) via phloem loading. The plant's entire source-to-sink relationship is regulated by multiple transporting proteins in a highly sophisticated manner and driven based on different stages of plant growth and development (PG&D) and environmental changes. The MTs play a pivotal role in PG&D in terms of increased plant height, branches/tiller numbers, enhanced numbers, length and filled panicles per plant, seed yield and grain quality. Dynamic climatic changes disturbed ionic balance (salt, drought and heavy metals) and sugar supply (cold and heat stress) in plants. Due to poor selectivity, some of the MTs also uptake toxic elements in roots negatively impact PG&D and are later on also exported to upper parts where they deteriorate grain quality. As an adaptive strategy, in response to salt and heavy metals, plants activate plasma membranes and vacuolar membrane-localized MTs that export toxic elements into vacuole and also translocate in the root's tips and shoot. However, in case of drought, cold and heat stresses, MTs increased water and sugar supplies to all organs. In this review, we mainly review recent literature from Arabidopsis, halophytes and major field crops such as rice, wheat, maize and oilseed rape in order to argue the global role of MTs in PG&D, and abiotic stress tolerance. We also discussed gene expression level changes and genomic variations within a species as well as within a family in response to developmental and environmental cues.

Mix and match: Patchwork domain evolution of the land plant-specific Ca2+-permeable mechanosensitive channel MCA

Multidomain proteins can have a complex evolutionary history that may involve de novo domain evolution, recruitment and / or recombination of existing domains and domain losses. Here, the domain evolution of the plant-specific Ca²⁺-permeable mechanosensitive channel protein, MID1-COMPLEMENTING ACTIVITY (MCA), was investigated. MCA, a multidomain protein, possesses a Ca²⁺-influx-MCA^func domain and a PLAC8 domain. Profile Hidden Markov Models (HMMs) of domains were assessed in 25 viridiplantae proteomes. While PLAC8 was detected in plants, animals, and fungi, MCA^func was found in streptophytes but not in chlorophytes. Full MCA proteins were only found in embryophytes. We identified the MCA^func domain in all streptophytes including charophytes where it appeared in E3 ubiquitin ligase-like proteins. Our Maximum Likelihood (ML) analyses suggested that the MCA^func domain evolved early in the history of streptophytes. The PLAC8 domain showed similarity to Plant Cadmium Resistance (PCR) genes, and the coupling of MCA^func and PLAC8 seemed to represent a single evolutionary event. This combination is unique in MCA, and does not exist in other plant mechanosensitive channels. Within angiosperms, gene duplications increased the number of MCAs. Considering their role in mechanosensing in roots, MCA might be instrumental for the rise of land plants. This study provides a textbook example of de novo domain emergence, recombination, duplication, and losses, leading to the convergence of function of proteins in plants.