Perception of karrikins by plants: a continuing enigma

Abstract Karrikins are small butenolide molecules with the capacity to promote germination and enhance seedling establishment. Generated abiotically from partial combustion of vegetation, karrikins are comparatively rare in the environment, but studying their mode of action has been most informative in revealing a new regulatory pathway for plant development that uses the karrikin perception machinery. Recent studies suggest that the karrikin receptor protein KAI2 and downstream transcriptional co-repressors in the SMXL family influence seed germination, seedling photomorphogenesis, root morphology, and responses to abiotic stress such as drought. Based on taxonomic distribution, this pathway is ubiquitous and likely to be evolutionarily ancient, originating prior to land plants. However, we still do not have a good grasp on how karrikins actually activate the receptor protein, and we have yet to discover the assumed endogenous ligand for KAI2 that karrikins are thought to mimic. This review covers recent progress in this field, as well as current gaps in our knowledge.

Download Full-text

MES7 Modulates Seed Germination via Regulating Salicylic Acid Content in Arabidopsis

Plants ◽

10.3390/plants10050903 ◽

2021 ◽

Vol 10 (5) ◽

pp. 903

Author(s):

Wenrui Gao ◽

Yan Liu ◽

Juan Huang ◽

Yaqiu Chen ◽

Chen Chen ◽

...

Keyword(s):

Salicylic Acid ◽

Salt Stress ◽

Abiotic Stress ◽

Seed Germination ◽

Environmental Conditions ◽

Acid Content ◽

Hydrolytic Enzyme ◽

Stress Conditions ◽

Transitional Period ◽

Highly Sensitive

Seed germination is an important phase transitional period of angiosperm plants during which seeds are highly sensitive to different environmental conditions. Although seed germination is under the regulation of salicylic acid (SA) and other hormones, the molecular mechanism underlying these regulations remains mysterious. In this study, we determined the expression of SA methyl esterase (MES) family genes during seed germination. We found that MES7 expression decreases significantly in imbibed seeds, and the dysfunction of MES7 decreases SA content. Furthermore, MES7 reduces and promotes seed germination under normal and salt stress conditions, respectively. The application of SA restores the seed germination deficiencies of mes7 mutants under different conditions. Taking together, our observations uncover a MeSA hydrolytic enzyme, MES7, regulates seed germination via altering SA titer under normal and abiotic stress conditions.

Download Full-text

BrEXLB1, a Brassica rapa Expansin-Like B1 Gene Is Associated with Root Development, Drought Stress Response, and Seed Germination

Genes ◽

10.3390/genes11040404 ◽

2020 ◽

Vol 11 (4) ◽

pp. 404 ◽

Cited By ~ 2

Author(s):

Muthusamy Muthusamy ◽

Joo Yeol Kim ◽

Eun Kyung Yoon ◽

Jin A. Kim ◽

Soo In Lee

Keyword(s):

Abiotic Stress ◽

Drought Stress ◽

Stress Response ◽

Seed Germination ◽

Drought Tolerance ◽

Root Growth ◽

Brassica Rapa ◽

Root Development ◽

Clubroot Disease ◽

Qrt Pcr

Expansins are structural proteins prevalent in cell walls, participate in cell growth and stress responses by interacting with internal and external signals perceived by the genetic networks of plants. Herein, we investigated the Brassica rapa expansin-like B1 (BrEXLB1) interaction with phytohormones (IAA, ABA, Ethephon, CK, GA3, SA, and JA), genes (Bra001852, Bra001958, and Bra003006), biotic (Turnip mosaic Virus (TuMV), Pectobacterium carotovorum, clubroot disease), and abiotic stress (salt, oxidative, osmotic, and drought) conditions by either cDNA microarray or qRT-PCR assays. In addition, we also unraveled the potential role of BrEXLB1 in root growth, drought stress response, and seed germination in transgenic Arabidopsis and B. rapa lines. The qRT-PCR results displayed that BrEXLB1 expression was differentially influenced by hormones, and biotic and abiotic stress conditions; upregulated by IAA, ABA, SA, ethylene, drought, salt, osmotic, and oxidative conditions; and downregulated by clubroot disease, P. carotovorum, and TuMV infections. Among the tissues, prominent expression was observed in roots indicating the possible role in root growth. The root phenotyping followed by confocal imaging of root tips in Arabidopsis lines showed that BrEXLB1 overexpression increases the size of the root elongation zone and induce primary root growth. Conversely, it reduced the seed germination rate. Further analyses with transgenic B. rapa lines overexpressing BrEXLB1 sense (OX) and antisense transcripts (OX-AS) confirmed that BrEXLB1 overexpression is positively associated with drought tolerance and photosynthesis during vegetative growth phases of B. rapa plants. Moreover, the altered expression of BrEXLB1 in transgenic lines differentially influenced the expression of predicted BrEXLB1 interacting genes like Bra001852 and Bra003006. Collectively, this study revealed that BrEXLB1 is associated with root development, drought tolerance, photosynthesis, and seed germination.

Download Full-text

Genome-wide association study uncovers new genetic loci and candidate genes underlying seed chilling-germination in maize

PeerJ ◽

10.7717/peerj.11707 ◽

2021 ◽

Vol 9 ◽

pp. e11707

Author(s):

Yinchao Zhang ◽

Peng Liu ◽

Chen Wang ◽

Na Zhang ◽

Yuxiao Zhu ◽

...

Keyword(s):

Abiotic Stress ◽

Seed Germination ◽

Association Study ◽

Candidate Genes ◽

Molecular Mechanisms ◽

Genome Wide Association Study ◽

Chilling Stress ◽

Nucleotide Polymorphisms ◽

Plant Tolerance ◽

Multiple Traits

As one of the major crops, maize (Zea mays L.) is mainly distributed in tropical and temperate regions. However, with the changes of the environments, chilling stress has become a significantly abiotic stress affecting seed germination and thus the reproductive and biomass accumulation of maize. Herein, we investigated five seed germination-related phenotypes among 300 inbred lines under low-temperature condition (10 °C). By combining 43,943 single nucleotide polymorphisms (SNPs), a total of 15 significant (P < 2.03 × 10-6) SNPs were identified to correlate with seed germination under cold stress based on the FarmCPU model in GWAS, among which three loci were repeatedly associated with multiple traits. Ten gene models were closely linked to these three variations, among which Zm00001d010454, Zm00001d010458, Zm00001d010459, and Zm00001d050021 were further verified by candidate gene association study and expression pattern analysis. Importantly, these candidate genes were previously reported to involve plant tolerance to chilling stress and other abiotic stress. Our findings contribute to the understanding of the genetic and molecular mechanisms underlying chilling germination in maize.

Download Full-text