Wounding induces the parallel activation of two signaling cascades: a MKK4/5-MPK3/6 module (rapid) and a jasmonic acid-dependent MAP3K14-MKK3-MPK1/2/7/14 module

The plant phytohormone ethylene regulates numerous physiological processes and contributes to plant–microbe interactions. Plants induce ethylene production to ward off pathogens after recognition of conserved microbe-associated molecular patterns (MAMPs). However, plant immune responses against pathogens are essentially not different from those triggered by neutral and beneficial microbes. Recent studies indicate that ethylene is an important factor for beneficial plant–microbial association under abiotic stress such as salt and heat stress. The association of beneficial microbes with plants under abiotic stresses modulates ethylene levels which control the expression of ethylene-responsive genes (ERF), and ERFs further regulate the plant transcriptome, epi-transcriptome, Na⁺/K⁺ homeostasis and antioxidant defense mechanisms against reactive oxygen species (ROS). Understanding ethylene-dependent plant–microbe interactions is crucial for the development of new strategies aimed at enhancing plant tolerance to harsh environmental conditions. In this review, we underline the importance of ethylene in beneficial plant–microbe interaction under abiotic stresses.

Post-transcriptional regulation of mRNA mediated by methylation at the N⁶ position of adenine (N⁶-methyladenosine (m⁶A)) has profound effects on transcriptome regulation in plants. Focused studies across eukaryotes offer glimpses into the processes governed by m⁶A throughout developmental and disease states. However, we lack an understanding of the dynamics and the regulatory potential of m⁶A during biotic stress in plants. Here, we provide a comprehensive look into the effects of m⁶A on both the short-term and long-term response to pathogen signaling in Arabidopsis (Arabidopsis thaliana). We demonstrate that m⁶A-deficient plants are more resistant to bacterial and fungal pathogen infections and have altered immune responses. Furthermore, m⁶A deposition is specifically coordinated on transcripts involved in defense and immunity prior to and proceeding the pathogen signal flagellin. Consequently, the dynamic modulation of m⁶A on specific stress-responsive transcripts is correlated with changes in abundance and cleavage of these transcripts. Overall, we show that the m⁶A methylome is regulated prior to and during simulated and active pathogen stress and functions in the coordination and balancing of normal growth and pathogen responses.

Summary: TCP transcription factors are key regulators of angiosperm cell proliferation processes. It is unknown whether their regulatory growth capacities are conserved across land plants, which we examined in liverworts, one of the earliest diverging land plant lineages. We generated knockout mutants for MpTCP1, the single TCP‐P clade gene in Marchantia polymorpha, and characterized its function by conducting cell proliferation and morphological analyses as well as messenger RNA expression, transcriptome, chemical, and DNA binding studies. Mptcp1^ge lines show a reduced vegetative thallus growth and extra tissue formation in female reproductive structures. Additionally, mutant plants reveal increased hydrogen peroxide (H₂O₂) levels and an enhanced pigmentation in the thallus caused by formation of secondary metabolites, such as aminochromes. MpTCP1 proteins interact redox dependently with DNA and regulate the expression of a comprehensive redox network, comprising enzymes involved in H₂O₂ metabolism. MpTCP1 regulates Marchantia growth in a context‐dependent manner. Redox sensitivity of the DNA binding capacity of MpTCP1 proteins provides a mechanism to respond to altered redox conditions. Our data suggest that MpTCP1 activity could thereby have contributed to diversification of land plant morphologies and to adaptations to abiotic and biotic challenges, as experienced by liverworts during early land plant colonization.

Senescence is an important physiological process which directly affects many agronomic traits in plants. Senescence induces chlorophyll degradation, phytohormone changes, cellular structure damage, and altered gene regulation. Although these physiological outputs are well defined, the molecular mechanisms employed are not known. Using dark-induced leaf senescence (DILS) as the experimental system, we investigated the role of N⁶-methyladenosine (m⁶A) mRNA methylation during senescence in Arabidopsis (Arabidopsis thaliana). Plants compromised in m⁶A machinery components like METHYLTRANSFERASE A (mta mutant) and VIRILIZER1 (vir-1 mutant) showed an enhanced DILS phenotype. This was accompanied by compromised chloroplast and photosynthesis performance in mta as well as accumulation of senescence-promoting camalexin and phytohormone jasmonic acid after dark treatment. m⁶A levels increased during DILS and destabilized senescence-related transcripts thereby preventing premature aging. Due to inefficient decay, senescence-related transcripts like ORESARA1 (ORE1), SENESCENCE-ASSOCIATED GENE 21 (SAG21), NAC-like, activated by AP3/PI (NAP), and NONYELLOWING 1 (NYE1) over-accumulated in mta thereby causing accelerated senescence during DILS. Overall, our data propose that m⁶A modification is involved in regulating the biological response to senescence in plants, providing targets for engineering stress tolerance of crops.