Due to their sessile state, plants are inevitably affected by and respond to the external environment. So far, plants have developed multiple adaptation and regulation strategies to abiotic stresses. One such system is epigenetic regulation, among which DNA methylation is one of the earliest and most studied regulatory mechanisms, which can regulate genome functioning and induce plant resistance and adaption to abiotic stresses. In this review, we outline the most recent findings on plant DNA methylation responses to drought, high temperature, cold, salt, and heavy metal stresses. In addition, we discuss stress memory regulated by DNA methylation, both in a transient way and the long-term memory that could pass to next generations. To sum up, the present review furnishes an updated account of DNA methylation in plant responses and adaptations to abiotic stresses.

In some plants, exposure to stress can induce a memory response, which appears to play an important role in adaptation to recurrent stress environments. However, whether rice exhibits drought stress memory and the molecular mechanisms that might underlie this process have remained unclear. Here, we ensured that rice drought memory was established after cycles of mild drought and re-watering treatment, and studied gene expression by whole-transcriptome strand-specific RNA sequencing (ssRNA-seq). We detected 6,885 transcripts and 238 lncRNAs involved in the drought memory response, grouped into 16 distinct patterns. Notably, the identified genes of dosage memory generally did not respond to the initial drought treatment. Our results demonstrate that stress memory can be developed in rice under appropriate water deficient stress, and lncRNA, DNA methylation and endogenous phytohormones (especially abscisic acid) participate in rice short-term drought memory, possibly acting as memory factors to activate drought-related memory transcripts in pathways such as photosynthesis and proline biosynthesis, to respond to the subsequent stresses.

Ethyl methanesulfonate (EMS)-induced mutagenesis is a powerful tool to generate genetic resource for identifying untapped genes and characterizing the function of genes to understand the molecular basis of important agronomic traits. This review focuses on application of contemporary EMS mutagenesis in the field of plant development and abiotic stress tolerance research, with particular focuses on reviewing the mutation types, mutagenesis site, mutagen concentration, mutagenesis duration, the identification and characterization of mutations responsible for altered stress tolerance responses. The application of EMS mutation breeding combined with genetic engineering in the future plant breeding and fundamental research was also discussed. The collective information in this review will provide good insight on how EMS mutagenesis is efficiently applied to improve abiotic stress tolerance of crops with the utilization of Next-generation sequencing (NGS) for mutation identification.

Plant cis-elements play important roles in global regulation of gene expression. Based on microarray data from rice flag leaves during early senescence, we identified W-box and G-box cis-elements as positive regulators of senescence in the important rice variety Minghui 63. Both cis-elements were bound by leaf senescence-specific proteins in vitro and influenced senescence in vivo. Furthermore, combination of the two elements drove enhanced expression during leaf senescence and copy numbers of the cis-elements significantly affected the levels of expression. The W-box is the cognate cis-element for WRKY proteins, while the G-box is the cognate cis-element for bZIP, bHLH and NAC proteins. Consistent with this, WRKY, bZIP, bHLH and NAC family members were overrepresented among transcription factor genes up-regulated according during senescence. Crosstalk between ABA, CTK, BR, auxin, GA and JA during senescence was uncovered by comparing expression patterns of senescence up-regulated transcription factors. Together, our results indicate that hormone-mediated signaling could converge on leaf senescence at the transcriptional level through W-box and G-box elements. Considering that there are very few documented early senescence-related cis-elements, our results significantly contribute to understanding the regulation of flag leaf senescence and provide prioritized targets for stay-green trait improvement.

Hsp70s (heat shock protein 70s) are a class of molecular chaperones that are highly conserved and ubiquitous in organisms ranging from microorganisms to plants and humans. Most research on Hsp70s has focused on the mechanisms of their functions as molecular chaperones, but recently, studies on stress responses are coming to the forefront. Hsp70s play key roles in cellular development and protecting living organisms from environmental stresses such as heat, drought, salinity, acidity, and cold. Moreover, functions of human Hsp70s are related to diseases including neurological disorders, cancer, and virus infection. In this review, we provide an overview of the specific roles of Hsp70s in response to stress, particularly abiotic stress, in all living organisms.