Molecular Characterization and Functional Analysis of Two Petunia PhEILs

OsEIN2-OsEIL1/2 pathway negatively regulates chilling tolerance by attenuating OsICE1 function in rice

Low temperature severely affects rice development and yield. Ethylene signal is essential for plant development and stress response. Here, we reported that the OsEIN2-OsEIL1/2 pathway reduced OsICE1-dependent chilling tolerance in rice. The overexpressing plants of OsEIN2, OsEIL1 and OsEIL2 exhibited severe stress symptoms with excessive reactive oxygen species (ROS) accumulation under chilling, while the mutants (osein2 and oseil1) and OsEIL2-RNA interference plants (OsEIL2-Ri) showed the enhanced chilling tolerance. We validated that OsEIL1 and OsEIL2 could form a heterxodimer and synergistically repressed OsICE1 expression by binding to its promoter. The expression of OsICE1 target genes, ROS scavenging- and photosynthesis-related genes were downregulated by OsEIN2 and OsEIL1/2, which were activated by OsICE1, suggesting that OsEIN2-OsEIL1/2 pathway might mediate ROS accumulation and photosynthetic capacity under chilling by attenuating OsICE1 function. Moreover, the association analysis of the seedling chilling tolerance with the haplotype showed that the lower expression of OsEIL1 and OsEIL2 caused by natural variation might confer chilling tolerance on rice seedlings. Finally, we generated OsEIL2-edited rice with an enhanced chilling tolerance. Taken together, our findings reveal a possible mechanism integrating OsEIN2-OsEIL1/2 pathway with OsICE1-dependent cascade in regulating chilling tolerance, providing a practical strategy for breeding chilling-tolerant rice.

Signalling cascades choreographing petal cell death: implications for postharvest quality

Senescence is a multifaceted and dynamic developmental phase pivotal in the plant's lifecycle, exerting significant influence and involving intricate regulatory mechanisms marked by a variety of structural, biochemical and molecular alterations. Biochemical changes, including reactive oxygen species (ROS) generation, membrane deterioration, nucleic acid degradation and protein degradation, characterize flower senescence. The progression of senescence entails a meticulously orchestrated network of interconnected molecular mechanisms and signalling pathways, ensuring its synchronized and efficient execution. Within flowering plants, petal senescence emerges as a crucial aspect significantly impacting flower longevity and postharvest quality, emphasizing the pressing necessity of unravelling the underlying signalling cascades orchestrating this process. Understanding the complex signalling pathways regulating petal senescence holds paramount importance, not only shedding light on the broader phenomenon of plant senescence but also paving the way for the development of targeted strategies to enhance the postharvest longevity of cut flowers. Various signalling pathways participate in petal senescence, encompassing hormone signalling, calcium signalling, protein kinase signalling and ROS signalling. Among these, the ethylene signalling pathway is extensively studied, and the manipulation of genes associated with ethylene biosynthesis or signal transduction has demonstrated the potential to enhance flower longevity. A thorough understanding of these complex pathways is critical for effectively delaying flower senescence, thereby enhancing postharvest quality and ornamental value. Therefore, this review adopts a viewpoint that combines fundamental research into the molecular intricacies of senescence with a practical orientation towards developing strategies for improving the postharvest quality of cut flowers. The innovation of this review is to shed light on the pivotal signalling cascades underpinning flower senescence and offer insights into potential approaches for modulating these pathways to postpone petal senescence in ornamental plants.

CRISPR/Cas9-mediated mutation of Eil1 transcription factor genes affects exogenous ethylene tolerance and early flower senescence in Campanula portenschlagiana

Improving tolerance to ethylene-induced early senescence of flowers and fruits is of major economic importance for the ornamental and food industry. Genetic modifications of genes in the ethylene-signalling pathway have frequently resulted in increased tolerance but often with unwanted side effects. Here, we used CRISPR/Cas9 to knockout the function of two CpEil1 genes expressed in flowers of the diploid ornamental plant Campanula portenschlagiana. The ethylene tolerance in flowers of the primary mutants with knockout of only one or all four alleles clearly showed increased tolerance to exogenous ethylene, although lower tolerance was obtained with one compared to four mutated alleles. The allele dosage effect was confirmed in progenies where flowers of plants with zero, one, two, three and four mutated alleles showed increasing ethylene tolerance. Mutation of the Cpeil1 alleles had no significant effect on flower longevity and endogenous flower ethylene level, indicating that CpEil1 is not involved in age-dependent senescence of flowers. The study suggests focus on EIN3/Eils expressed in the organs subjected to early senescence for obtaining tolerance towards exogenous ethylene. Furthermore, the observed allelic dosage effect constitutes a key handle for a gradual regulation of sensitivity towards exogenous ethylene, simultaneously monitoring possibly unwanted side effects.

CRISPR/Cas9 System: A Potential Tool for Genetic Improvement in Floricultural Crops

Demand of flowers is increasing with time worldwide. Floriculture has become one of the most important commercial trades in agriculture. Although traditional breeding methods like hybridization and mutation breeding have contributed significantly to the development of important flower varieties, flower production and quality of flowers can be significantly improved by employing modern breeding approaches. Novel traits of significance have interest to consumers and producers, such as fragrance, new floral color, change in floral architecture and morphology, vase life, aroma, and resistance to biotic and abiotic stresses, have been introduced by genetic manipulation. The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) system has recently emerged as a powerful genome-editing tool for accurately changing DNA sequences at specific locations. It provides excellent means of genetically improving floricultural crops. CRISPR/Cas system has been utilized in gene editing in horticultural cops. There are few reports on the utilization of the CRISPR/Cas9 system in flowers. The current review summarizes the research work done by employing the CRISPR/Cas9 system in floricultural crops including improvement in flowering traits such as color modification, prolonging the shelf life of flowers, flower initiation, and development, changes in color of ornamental foliage by genome editing. CRISPR/Cas9 gene editing could be useful in developing novel cultivars with higher fragrance and enhanced essential oil and many other useful traits. The present review also highlights the basic mechanism and key components involved in the CRISPR/Cas9 system.

Phosphoproteome analysis reveals the involvement of protein dephosphorylation in ethylene-induced corolla senescence in petunia

BACKGROUND

Senescence represents the last stage of flower development. Phosphorylation is the key posttranslational modification that regulates protein functions, and kinases may be more required than phosphatases during plant growth and development. However, little is known about global phosphorylation changes during flower senescence.

RESULTS

In this work, we quantitatively investigated the petunia phosphoproteome following ethylene or air treatment. In total, 2170 phosphosites in 1184 protein groups were identified, among which 2059 sites in 1124 proteins were quantified. To our surprise, treatment with ethylene resulted in 697 downregulated and only 117 upregulated phosphosites using a 1.5-fold threshold (FDR < 0.05), which showed that ethylene negatively regulates global phosphorylation levels and that phosphorylation of many proteins was not necessary during flower senescence. Phosphoproteome analysis showed that ethylene regulates ethylene and ABA signalling transduction pathways via phosphorylation levels. One of the major targets of ethylene-induced dephosphorylation is the plant mRNA splicing machinery, and ethylene treatment increases the number of alternative splicing events of precursor RNAs in petunia corollas.

CONCLUSIONS

Protein dephosphorylation could play an important role in ethylene-induced senescence, and ethylene treatment increased the number of AS precursor RNAs in petunia corollas.

Petal senescence: a hormone view

Flowers are highly complex organs that have evolved to enhance the reproductive success of angiosperms. As a key component of flowers, petals play a vital role in attracting pollinators and ensuring successful pollination. Having fulfilled this function, petals senesce through a process that involves many physiological and biochemical changes that also occur during leaf senescence. However, petal senescence is distinct, due to the abundance of secondary metabolites in petals and the fact that petal senescence is irreversible. Various phytohormones are involved in regulating petal senescence, and are thought to act both synergistically and antagonistically. In this regard, there appears to be developmental point during which such regulatory signals are sensed and senescence is initiated. Here, we review current understanding of petal senescence, and discuss associated regulatory mechanisms involving hormone interactions and epigenetic regulation.

Genome-wide identification and expression profiling of EIL gene family in woody plant representative poplar (Populus trichocarpa)

This study aimed to improve current understanding on ethylene-insensitive 3-like (EIL) members, least explored in woody plants such as poplar (Populus trichocarpa Torr. & Grey). Herein, seven putative EIL members were identified in P. trichocarpa genome and were roughly annotated either as EIN3-like sequence associated with ethylene pathway or EIL3-like sequences related with sulfur (S)-pathway. Motif-distribution pattern of proteins also corroborated this annotation. They were distributed on six chromosomes (chr1, 3, 4 and 8-10), and were revealed to encode a protein of 509-662 residues with nuclear localization. The presence of ethylene insensitive 3 (EIN3; PF04873) domain (covering first 80-280 residues from N-terminus) was confirmed by Hidden Markov Model-based search. The first half of EIL proteins (∼80-280 residues including EIN3 domain) was substantially conserved. The second half (∼300-600 residues) was considerably diverged. Additionally, first half of proteins harbored acidic, proline-rich and glutamine-rich sites, and supported the essentiality of these regions in the transcriptional-activation and protein-function. Moreover, identified six segmental and one-tandem duplications demonstrated the negative or purifying selective nature of mutations. Furthermore, expression profile analysis indicated the possibility of a crosstalk between EIN3- and EIL3-like genes, and co-expression networks implicated their interactions with very diverse panels of biological molecules.