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The homeostasis of histone methylation is maintained by histone methyltransferases and demethylases, which are important for the regulation of gene expression. Here, we report a histone demethylase from rice (Oryza sativa), Jumonji C domain-containing protein (JMJ710), which belongs to the JMJD6 group and plays an important role in the response to drought stress. Overexpression of JMJ710 causes a drought-sensitive phenotype, while RNAi and clustered regularly interspaced short palindromic repeats (CRISPR)-knockout mutant lines show drought tolerance. In vitro and in vivo assays showed that JMJ710 is a histone demethylase. It targets to MYB TRANSCRIPTION FACTOR 48 (MYB48-1) chromatin, demethylates H3K36me2, and negatively regulates the expression of MYB48-1, a positive regulator of drought tolerance. Under drought stress, JMJ710 is downregulated and the expression of MYB48-1 increases, and the subsequent activation of its downstream drought-responsive genes leads to drought tolerance. This research reports a negative regulator of drought stress-responsive genes, JMJ710, that ensures that the drought tolerance mechanism is not mis-activated under normal conditions but allows quick activation upon drought stress.

Plastid isoprenoids, a diverse group of compounds that includes carotenoids, chlorophylls, tocopherols, and multiple hormones, are essential for plant growth and development. Here, we identified and characterized SEED CAROTENOID DEFICIENT (SCD), which encodes an enzyme that functions in the biosynthesis of plastid isoprenoids in maize (Zea mays). SCD converts 2C-methyl-d-erytrithol 2,4-cyclodiphosphate to 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate in the penultimate step of the methylerythritol phosphate (MEP) pathway. In scd mutants, plant growth and development are impaired and the levels of MEP-derived isoprenoids, such as carotenoids, chlorophylls, and tocopherols, as well as abscisic and gibberellic acids, are reduced in leaves and seeds. This scd metabolic alteration varies among plant tissues and under different light conditions. RNA-sequencing of the scd mutant and wild type identified a limited number of differentially expressed genes in the MEP pathway, although isoprenoid levels were significantly reduced in scd seeds and dark-grown leaves. Furthermore, SCD-overexpressing transgenic lines showed little or no differences in isoprenoid levels, indicating that SCD may be subject to posttranslational regulation or not represent a rate-limiting step in the MEP pathway. These results enhance our understanding of the transcriptomic and metabolic regulatory roles of enzymes in the MEP pathway and of their effects on downstream isoprenoid pathways in various plant tissues and under different light conditions.