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A dynamic assembly of nuclear and cytoplasmic processes regulate gene activity. Hypoxic stress and the associated energy crisis activate a plurality of regulatory mechanisms including modulation of chromatin structure, transcriptional activation and post‐transcriptional processes. Temporal control of genes is associated with specific chromatin modifications and transcription factors. Genome‐scale technologies that resolve transcript subpopulations in the nucleus and cytoplasm indicate post‐transcriptional processes enable cells to conserve energy, prepare for prolonged stress and accelerate recovery. Moreover, the harboring of gene transcripts associated with growth in the nucleus and macromolecular RNA–protein complexes contributes to the preferential translation of stress‐responsive gene transcripts during hypoxia. We discuss evidence of evolutionary variation in integration of nuclear and cytoplasmic processes that may contribute to variations in flooding resilience.

 

Understanding the impact of elevated CO₂(eCO₂) in global agriculture is important given climate change projections. Breeding climate‐resilient crops depends on genetic variation within naturally varying populations. The effect of genetic variation in response to eCO₂is poorly understood, especially in crop species. We describe the different ways in whichSolanum lycopersicumand its wild relativeS. pennelliirespond to eCO₂, from cell anatomy, to the transcriptome, and metabolome. We further validate the importance of translational regulation as a potential mechanism for plants to adaptively respond to rising levels of atmospheric CO₂.

 

The basic unit of chromatin, the nucleosome, is an octamer of four core histone proteins (H2A, H2B, H3, and H4) and serves as a fundamental regulatory unit in all DNA-templated processes. The majority of nucleosome assembly occurs during DNA replication when these core histones are produced en masse to accommodate the nascent genome. In addition, there are a number of nonallelic sequence variants of H2A and H3 in particular, known as histone variants, that can be incorporated into nucleosomes in a targeted and replication-independent manner. By virtue of their sequence divergence from the replication-coupled histones, these histone variants can impart unique properties onto the nucleosomes they occupy and thereby influence transcription and epigenetic states, DNA repair, chromosome segregation, and other nuclear processes in ways that profoundly affect plant biology. In this review, we discuss the evolutionary origins of these variants in plants, their known roles in chromatin, and their impacts on plant development and stress responses. We focus on the individual and combined roles of histone variants in transcriptional regulation within euchromatic and heterochromatic genome regions. Finally, we highlight gaps in our understanding of plant variants at the molecular, cellular, and organismal levels, and we propose new directions for study in the field of plant histone variants. 

An increase in nutrient dose leads to proportional increases in crop biomass and agricultural yield. However, the molecular underpinnings of this nutrient dose–response are largely unknown. To investigate, we assayed changes in the Arabidopsis root transcriptome to different doses of nitrogen (N)—a key plant nutrient—as a function of time. By these means, we found that rate changes of genome-wide transcript levels in response to N-dose could be explained by a simple kinetic principle: the Michaelis–Menten (MM) model. Fitting the MM model allowed us to estimate the maximum rate of transcript change ( V max ), as well as the N-dose at which one-half of V max was achieved ( K m ) for 1,153 N-dose–responsive genes. Since transcription factors (TFs) can act in part as the catalytic agents that determine the rates of transcript change, we investigated their role in regulating N-dose–responsive MM-modeled genes. We found that altering the abundance of TGA1, an early N-responsive TF, perturbed the maximum rates of N-dose transcriptomic responses ( V max ), K m , as well as the rate of N-dose–responsive plant growth. We experimentally validated that MM-modeled N-dose–responsive genes included both direct and indirect TGA1 targets, using a root cell TF assay to detect TF binding and/or TF regulation genome-wide. Taken together, our results support a molecular mechanism of transcriptional control that allows an increase in N-dose to lead to a proportional change in the rate of genome-wide expression and plant growth.