Abscisic acid (ABA) is an important phytohormone regulating plant growth, development, and stress responses. It has an essential role in multiple physiological processes of plants, such as stomatal ...closure, cuticular wax accumulation, leaf senescence, bud dormancy, seed germination, osmotic regulation, and growth inhibition among many others. Abscisic acid controls downstream responses to abiotic and biotic environmental changes through both transcriptional and posttranscriptional mechanisms. During the past 20 years, ABA biosynthesis and many of its signaling pathways have been well characterized. Here we review the dynamics of ABA metabolic pools and signaling that affects many of its physiological functions.
Abscisic acid (ABA) is the major stress hormone that coordinates plant growth, development and abiotic stress responses. In this review, we summarized the recent progresses on its metabolism, transport and signaling, and discussed the open questions about ABA dynamics and functions.
In eukaryotic cells, gene expression is greatly influenced by the dynamic chromatin environment. Epigenetic mechanisms, including covalent modifications to DNA and histone tails and the accessibility ...of chromatin, create various chromatin states for stress‐responsive gene expression that is important for adaptation to harsh environmental conditions. Recent studies have revealed that many epigenetic factors participate in abiotic stress responses, and various chromatin modifications are changed when plants are exposed to stressful environments. In this review, we summarize recent progress on the cross‐talk between abiotic stress response pathways and epigenetic regulatory pathways in plants. Our review focuses on epigenetic regulation of plant responses to extreme temperatures, drought, salinity, the stress hormone abscisic acid, nutrient limitations and ultraviolet stress, and on epigenetic mechanisms of stress memory.
Epigenetic mechanisms create various chromatin states for gene expression that is important for adaptation to harsh environmental conditions. Recent studies have revealed important involvements of epigenetic mechanisms in plant abiotic stress responses. This review summarizes recent progress on the cross‐talk between abiotic stress responses and epigenetic regulatory pathways in plants.
A major problem facing humanity is that our numbers are growing but the availability of land and fresh water for agriculture is not. This problem is being exacerbated by climate change-induced ...increases in drought, and other abiotic stresses. Stress-resistant crops are needed to ensure yield stability under stress conditions and to minimize the environmental impacts of crop production. Evolution has created thousands of species of naturally stress-resistant plants (NSRPs), some of which have already been subjected to human domestication and are considered minor crops. Broader cultivation of these minor crops will diversify plant agriculture and the human diet, and will therefore help improve global food security and human health. More research should be directed toward understanding and utilizing NSRPs. Technologies are now available that will enable researchers to rapidly improve the genetics of NSRPs, with the goal of increasing NSRP productivity while retaining NSRP stress resistance and nutritional value.
Recently, DNA methylation was proposed to regulate fleshy fruit ripening. Fleshy fruits can be distinguished by their ripening process as climacteric fruits, such as tomatoes, or non-climacteric ...fruits, such as strawberries. Tomatoes undergo a global decrease in DNA methylation during ripening, due to increased expression of a DNA demethylase gene. The dynamics and biological relevance of DNA methylation during the ripening of non-climacteric fruits are unknown.
Here, we generate single-base resolution maps of the DNA methylome in immature and ripe strawberry. We observe an overall loss of DNA methylation during strawberry fruit ripening. Thus, ripening-induced DNA hypomethylation occurs not only in climacteric fruit, but also in non-climacteric fruit. Application of a DNA methylation inhibitor causes an early ripening phenotype, suggesting that DNA hypomethylation is important for strawberry fruit ripening. The mechanisms underlying DNA hypomethylation during the ripening of tomato and strawberry are distinct. Unlike in tomatoes, DNA demethylase genes are not upregulated during the ripening of strawberries. Instead, genes involved in RNA-directed DNA methylation are downregulated during strawberry ripening. Further, ripening-induced DNA hypomethylation is associated with decreased siRNA levels, consistent with reduced RdDM activity. Therefore, we propose that a downregulation of RdDM contributes to DNA hypomethylation during strawberry ripening.
Our findings provide new insight into the DNA methylation dynamics during the ripening of non-climacteric fruit and suggest a novel function of RdDM in regulating an important process in plant development.
Previous studies on base editing in dicots showed that improvement of nCas9 expression level could significantly increase the editing efficiency (Kang et al., 2018). ...we sought to optimize pCXPE01 ...to improve editing efficiency by increasing nCas9‐MMLV expression level. According to the sequencing results, we detected desired edits at two genes, ALS2 and PDS1. ...no plant phenotype results were reported in these studies. ...our prime‐edited T0 tomato plants were chimeras and did not display any obvious phenotypes (Figure 1e, g and h). ...for both monocots and dicots, assessment of the utility of prime editing awaits future analysis of large populations of edited lines and their off‐springs.
Small, non-coding RNAs are a distinct class of regulatory RNAs in plants and animals that control a variety of biological processes. In plants, several classes of small RNAs with specific sizes and ...dedicated functions have evolved through a series of pathways. The major classes of small RNAs include microRNAs (miRNAs) and small interfering RNAs (siRNAs), which differ in their biogenesis. miRNAs control the expression of cognate target genes by binding to reverse complementary sequences, resulting in cleavage or translational inhibition of the target RNAs. siRNAs have a similar structure, function, and biogenesis as miRNAs but are derived from long double-stranded RNAs and can often direct DNA methylation at target sequences. Besides their roles in growth and development and maintenance of genome integrity, small RNAs are also important components in plant stress responses. One way in which plants respond to environmental stress is by modifying their gene expression through the activity of small RNAs. Thus, understanding how small RNAs regulate gene expression will enable researchers to explore the role of small RNAs in biotic and abiotic stress responses. This review focuses on the regulatory roles of plant small RNAs in the adaptive response to stresses. This article is part of a Special Issue entitled: Plant gene regulation in response to abiotic stress.
► Small RNAs are important regulators of gene expression in plants and animals. ► Plant small RNAs play a role in biotic and abiotic stress responses. ► The expression of many miRNAs is responsive to various stresses. ► Stress-responsive small RNAs are crucial components in gene regulatory networks.
DNA methylation is an important epigenetic mark involved in diverse biological processes. In plants, DNA methylation can be established through the RNA-directed DNA methylation pathway, an RNA ...interference pathway for transcriptional gene silencing （TGS）, which requires 24-nt small interfering RNAs. In mammals, de novo DNA methylation occurs primarily at two developmental stages： during early embryogenesis and during gametogenesis. While it is not clear whether establishment of DNA methylation patterns in mammals involves RNA interference in general, de novo DNA methylation and suppression of transposons in germ cells require 24-32-nt piwi-interacting small RNAs. DNA methylation status is dynamically regulated by DNA methylation and demethylation reactions. In plants, active DNA demethylation relies on the repressor of silencing 1 family of bifunctional DNA glycosylases, which remove the 5-methylcytosine base and then cleave the DNA backbone at the abasic site, initiating a base excision repair （BER） pathway. In animals, multiple mechanisms of active DNA demethylation have been proposed, including a deaminase- and DNA glycosylase-initiated BER pathway. New information concerning the effects of various histone modifications on the establishment and maintenance of DNA methylation has broadened our understanding of the regulation of DNA methylation. The function of DNA methylation in plants and animals is also discussed in this review.
Dear Editor, The class 2/type Ⅱ clustered regularly interspaced short palindromic repeat （CRISPR）/Cas9 system has been used successfully for simultaneous modification of multiple loci in plants. Two ...general strategies have been applied to coexpress multiple single guide RNAs （sgRNAs） to achieve multiplex gene editing in plant cells.
The widespread agricultural problem of pre-harvest sprouting (PHS) could potentially be overcome by improving seed dormancy. Here, we report that miR156, an important grain yield regulator, also ...controls seed dormancy in rice. We found that mutations in one MIR156 subfamily enhance seed dormancy and suppress PHS with negligible effects on shoot architecture and grain size, whereas mutations in another MIR156 subfamily modify shoot architecture and increase grain size but have minimal effects on seed dormancy. Mechanistically, mir156 mutations enhance seed dormancy by suppressing the gibberellin (GA) pathway through de-represssion of the miR156 target gene Ideal Plant Architecture 1 (IPA1), which directly regulates multiple genes in the GA pathway. These results provide an effective method to suppress PHS without compromising productivity, and will facilitate breeding elite crop varieties with ideal plant architectures.
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