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Climate change and enhanced pollution levels are subjecting plants and crops to an increased number of different stressors, simultaneously or sequentially, generating conditions of multifactorial stress combination (MFSC). Although MFSC was shown to severely diminish plant growth, yield, and survival, how plants acclimate to increased levels of stress complexity is largely unknown. Here, we reveal that theArabidopsis thalianatranscriptional regulator basic helix-loop-helix 35 (bHLH35) is required for plant acclimation to a specific set of MFSC conditions that includes a combination of salinity, excess light, and heat, occurring simultaneously (but not to each of these stresses applied individually or in any other combination). Under the three-stress combination, bHLH35 interacts with no apical meristem/transcription activator factor/cup-shaped cotyledon 69 (NAC069), binds the promoter oflateral organ boundaries domain 31 (LBD31), and regulates the expression of transcripts involved in flavonoid metabolism and ethylene signaling. Our findings uncover a high degree of specificity in plant responses to stress combination, suggesting that different conditions of MFSC could require the function of specific genetic programs for acclimation. 

Nitric oxide (NO) is a key regulator of plant development, growth, and responses to the environment. Together with hydrogen peroxide (H₂O₂), NO modifies the structure and function of proteins, controlling redox signaling. Although NO has been studied extensively at the cellular and subcellular levels, very little is known about changes in NO content at the whole‐plant level.Here, we report on the development of an aboveground whole‐plant live imaging method for NO. Using mutants with altered NO levels, as well as an NO donor/scavenger, we demonstrate the specificity of the detection method for NO.Arabidopsis thalianaplants were found to produce a basal level of NO under control conditions. NO levels accumulated enzymatically in plants following heat stress applied to the entire plant, as well as in a systemic manner following different locally applied stimuli. Similar or opposing accumulation patterns were also found for NO and H₂O₂during the response of plants to different stimuli.Our findings reveal that NO accumulates during the systemic response of plants to a local stimulus. In addition, they shed new light on the intricate relationships between NO and H₂O₂. The new method reported opens the way for multiple future studies of NO's role in plant biology. 

Spatiotemporal regulation of gene expression by polycomb repressive complex 2 (PRC2) is critical for animal and plant development. The Arabidopsis fertilization independent seed (FIS)-PRC2 complex functions specifically during plant reproduction from gametogenesis to seed development. After a double fertilization event, triploid endosperm proliferates early, followed by the growth of a diploid embryo, which replaces the endosperm in Arabidopsis and many dicots. Key genes critical for endosperm proliferation such as IKU2 and MINI3 are activated after fertilization. Here we report that two MADS-box AGAMOUS-LIKE (AGL) proteins associate with the key endosperm proliferation loci and recruit the FIS-PRC2 repressive complex at 4–5 days after pollination (DAP). Interestingly, AGL9 and AGL15 only accumulate toward the end of endosperm proliferation at 4–5 DAP and promote the deposition of H3K27me3 marks at key endosperm proliferation loci. Disruption of AGL9 and AGL15 or overexpression of AGL9 or AGL15 significantly influence endosperm proliferation and cellularization. Genome-wide analysis with cleavage Under Targets and tagmentation (CUT&Tag) sequencing and RNA sequencing revealed the landscape of endosperm H3K27me3 marks and gene expression profiles in Col-0 and agl9 agl15. CUT&Tag qPCR also demonstrated the occupancy of the two MADS-box proteins and FIS-PRC2 on a few representative target loci. Our studies suggest that MADS-box proteins could potentially recruit PRC2 to regulate many other developmental processes in plants or even in fungi and animals.