Handling the Heat: Methylome Variation Underlying Heat Tolerance in Cotton

Methylation in DNA, histone, and RNA during flowering under stress condition: A review

Flowering is the most critical transition period in the whole lifecycle of plants, and it is a highly sensitive period to stress. New combinations of temperature, drought stress, carbon dioxide and other abiotic/biotic conditions resulting from contemporary climate change affect the flowering process. Plants have evolved several strategies to deal with environmental stresses, including epigenetic modifications. Numerous studies show that environmental stresses trigger methylation/demethylation during flowering to preserve/accelerate plant lifecycle. What's more, histone and DNA methylation can be induced to respond to stresses, resulting in changes of flowering gene expression and enhancing stress tolerance in plants. Furthermore, RNA methylation may influence stress-regulated flowering by regulating mRNA stability and antioxidant mechanism. Our review presents the involvement of methylation in stress-repressed and stress-induced flowering. The crosstalk between methylation and small RNAs, phytohormones and exogenous substances (such as salicylic acid, nitric oxide) during flowering under different stresses were discussed. The latest regulatory evidence of RNA methylation in stress-regulated flowering was collected for the first time. Meanwhile, the limited evidences of methylation in biotic stress-induced flowering were summarized. Thus, the review provides insights into understanding of methylation mechanism in stress-regulated flowering and makes use for the development of regulating plant flowering at epigenetic level in the future.

In Response to Abiotic Stress, DNA Methylation Confers EpiGenetic Changes in Plants

Epigenetics involves the heritable changes in patterns of gene expression determined by developmental and abiotic stresses, i.e., drought, cold, salinity, trace metals, and heat. Gene expression is driven by changes in DNA bases, histone proteins, the biogenesis of ncRNA, and changes in the nucleotide sequence. To cope with abiotic stresses, plants adopt certain changes driven by a sophisticated biological system. DNA methylation is a primary mechanism for epigenetic variation, which can induce phenotypic alterations in plants under stress. Some of the stress-driven changes in plants are temporary, while some modifications may be stable and inheritable to the next generations to allow them to cope with such extreme stress challenges in the future. In this review, we discuss the pivotal role of epigenetically developed phenotypic characteristics in plants as an evolutionary process participating in adaptation and tolerance responses to abiotic and biotic stresses that alter their growth and development. We emphasize the molecular process underlying changes in DNA methylation, differential variation for different species, the roles of non-coding RNAs in epigenetic modification, techniques for studying DNA methylation, and its role in crop improvement in tolerance to abiotic stress (drought, salinity, and heat). We summarize DNA methylation as a significant future research priority for tailoring crops according to various challenging environmental issues.

High temperature susceptibility of sexual reproduction in crop plants

Climate change-induced increases in the frequency of extreme weather events, particularly heatwaves, are a serious threat to crop productivity. The productivity of grain crops is dependent on the success of sexual reproduction, which is very sensitive to heat stress. Male gametophyte development has been identified as the most heat-vulnerable stage. This review outlines the susceptibility of the various stages of sexual reproduction in flowering plants from the time of floral transition to double fertilization. We summarize current knowledge concerning the molecular mechanisms underpinning the heat stress-induced aberrations and abnormalities at flowering, male reproductive development, female reproductive development, and fertilization. We highlight the stage-specific bottlenecks in sexual reproduction, which regulate seed set and final yields under high-temperature conditions, together with the outstanding research questions concerning genotypic and species-specific differences in thermotolerance observed in crops. This knowledge is essential for trait selection and genetic modification strategies for the development of heat-tolerant genotypes and high-temperature-resilient crops.