Cytokinin dehydrogenase/oxidase (CKX) enzymes play a key role in regulating cytokinin (CK) levels in plants by degrading the excess of this phytohormone. CKX genes have proven an attractive target for genetic engineering, as their silencing boosts cytokinin accumulation in various tissues, thereby contributing to a rapid increase in biomass and overall plant productivity. We previously reported a similar effect in finger millet (Eleusine coracana) somaclonal lines, caused by downregulation of EcCKX1 and EcCKX2. However, the CKX gene family has numerous representatives, especially in allopolyploid crop species, such as E. coracana. To date, the entire CKX gene family of E. coracana and its related species has not been characterized. We offer here, for the first time, a comprehensive genome-wide identification and analysis of a panel of CKX genes in finger millet. The functional genes identified in the E. coracana genome are compared with the previously-identified genes, EcCKX1 and EcCKX2. Exon-intron structural analysis and motif analysis of FAD- and CK-binding domains are performed. The phylogeny of the EcCKX genes suggests that CKX genes are divided into several distinct groups, corresponding to certain isotypes. Finally, the phenotypic effect of EcCKX1 and EcCKX2 in partially silencing the SE7 somaclonal line is investigated, showing that lines deficient in CKX-expression demonstrate increased grain yield and greater bushiness, enhanced biomass accumulation, and a shorter vegetation cycle.

/pdf/genome-wide-identification-and-analysis-of-the-cytokinin-2izg9v90.pdf

Genome-wide identification and analysis of the cytokinin oxidase/dehydrogenase (ckx) gene family in finger millet (Eleusine coracana)

Cytokinin oxidase/dehydrogenase (CKX) irreversibly degrades cytokinin, regulates growth and development, and helps plants to respond to environmental stress. Although the CKX gene has been well characterized in various plants, its role in soybean remains elusive. Therefore, in this study, the evolutionary relationship, chromosomal location, gene structure, motifs, cis-regulatory elements, collinearity, and gene expression patterns of GmCKXs were analyzed using RNA-seq, quantitative real-time PCR (qRT-PCR), and bioinformatics. We identified 18 GmCKX genes from the soybean genome and grouped them into five clades, each comprising members with similar gene structures and motifs. Cis-acting elements involved in hormones, resistance, and physiological metabolism were detected in the promoter regions of GmCKXs. Synteny analysis indicated that segmental duplication events contributed to the expansion of the soybean CKX family. The expression profiling of the GmCKXs genes using qRT-PCR showed tissue-specific expression patterns. The RNA-seq analysis also indicated that GmCKXs play an important role in response to salt and drought stresses at the seedling stage. The responses of the genes to salt, drought, synthetic cytokinin 6-benzyl aminopurine (6-BA), and the auxin indole-3-acetic acid (IAA) at the germination stage were further evaluated by qRT-PCR. Specifically, the GmCKX14 gene was downregulated in the roots and the radicles at the germination stage. The hormones 6-BA and IAA repressed the expression levels of GmCKX1, GmCKX6, and GmCKX9 genes but upregulated the expression levels of GmCKX10 and GmCKX18 genes. The three abiotic stresses also decreased the zeatin content in soybean radicle but enhanced the activity of the CKX enzymes. Conversely, the 6-BA and IAA treatments enhanced the CKX enzymes’ activity but reduced the zeatin content in the radicles. This study, therefore, provides a reference for the functional analysis of GmCKXs in soybean in response to abiotic stresses.

https://www.frontiersin.org/articles/10.3389/fpls.2023.1163219/pdf

Genome-wide identification of the soybean cytokinin oxidase/dehydrogenase gene family and its diverse roles in response to multiple abiotic stress

The development of high-yielding, bio-fortified, stress-tolerant crop cultivars is the need of the hour in the wake of increasing global food insecurity, abrupt climate change, and continuous shrinking of resources and landmass suitable for agriculture. The cytokinin group of phytohormones positively regulates seed yield by simultaneous regulation of source capacity (leaf senescence) and sink strength (grain number and size). Cytokinins also regulate root-shoot architecture by promoting shoot growth and inhibiting root growth. Cytokinin oxidase/dehydrogenase (CKX) are the only enzymes that catalyze the irreversible degradation of active cytokinins and thus negatively regulate the endogenous cytokinin levels. Genetic manipulation of CKX genes is the key to improve seed yield and root-shoot architecture through direct manipulation of endogenous cytokinin levels. Downregulation of CKX genes expressed in sink tissues such as inflorescence meristem and developing seeds, through reverse genetics approaches such as RNAi and CRISPR/Cas9 resulted in increased yield marked by increased number and size of grains. On the other hand, root-specific expression of CKX genes resulted in decreased endogenous cytokinin levels in roots which in turn resulted in increased root growth indicated by increased root branching, root biomass, and root-shoot biomass ratio. Enhanced root growth provided enhanced tolerance to drought stress and improved micronutrient uptake efficiency. In this review, we have emphasized the role of CKX as a genetic factor determining yield, micronutrient uptake efficiency, and response to drought stress. We have summarised the efforts made to increase crop productivity and drought stress tolerance in different crop species through genetic manipulation of CKX family genes.

https://www.frontiersin.org/articles/10.3389/fgene.2022.941595/pdf

Killing two birds with a single stone—genetic manipulation of cytokinin oxidase/dehydrogenase (CKX) genes for enhancing crop productivity and amelioration of drought stress response

With the frequent occurrence of extreme natural disasters, unfavorable growth environment is a common phenomenon in the life cycle of plants. In recent years, universal stress proteins (USPs) have attracted extensive attention in the field of plant science for their expression patterns and functional analysis. However, the characterization of the USP family remains unclear in grape. In this study, we identified 30 VvUSPs in the grape genome, which could be divided into three classes according to their encoded protein sequences, and this classification was reflected by the distribution of conserved motifs. Gene duplication analysis demonstrated that segmental duplication was an important pathway in the expansion of the VvUSP family. The expression patterns of 12 VvUSPs were significantly different between tissues, implying they had different functions in various tissues. Cis-acting element and expression analysis showed that most of the promoter regions of VvUSPs contained sequences responsive to hormones and stress elements, especially the promoter region of VIT_16s0013g01920. In conclusion, our findings provide comprehensive information for the further investigation of the genetics and protein functions of the USP gene family in grape.

/pdf/genome-wide-identification-and-characterization-of-usp-gene-1cwz42mp.pdf

Genome-Wide Identification and Characterization of USP Gene Family in Grapes (Vitis vinifera L.)

Genome-wide association study reveals candidate genes for gummy stem blight resistance in cucumber

Genome-wide identification and analysis of cytokinin dehydrogenase/oxidase (CKX) family genes in Brassica oleracea L. reveals their involvement in response to Plasmodiophora brassicae infections

Genome-wide Identification and Analysis of Cytokinin Dehydrogenase/oxidase (CKX) Family Genes in Brassica oleracea L. Reveals Their Involvement in Response to Plasmodiophora brassicae Infections

The TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) gene family, a kind of plant specific transcription factor, is essential for stress response, cell growth, and cell proliferation. However, the characterization of TCP family is still not clear in Pak-choi [ Brassica campestris (syn. Brassica rapa ) ssp. chinensis var. communis ]. In this study, genome-wide analysis of TCP gene family was performed and 26 TCP genes were identified in Pak-choi. Phylogenetic analysis demonstrated that the 26 BcTCPs were divided into two classes: Class I and Class II. Class II was further classified into two subclasses, CIN and CYC/TB1. The qPCR results suggested that most BcTCPs respond to abiotic stresses. The expressions of BcTCP3 , BcTCP12 , BcTCP21 , and BcTCP22 were significantly changed under ABA and cold treatment. BcTCP3 and BcTCP12 were also up-regulated under osmotic treatment. Subcellular localization showed that BcTCP3 and BcTCP21 were located in the nucleus. Our results will facilitate revealing the functions and regulatory mechanisms of BcTCPs . 

Genome-Wide Identification and Characterization of TCP Family Genes in Pak-Choi [Brassica campestris (syn. Brassica rapa) ssp. chinensis var. communis]

Feng Wang

Papers

Genome-wide identification and analysis of cytokinin dehydrogenase/oxidase (CKX) family genes in Brassica oleracea L. reveals their involvement in response to Plasmodiophora brassicae infections

Genome-wide Identification and Analysis of Cytokinin Dehydrogenase/oxidase (CKX) Family Genes in Brassica oleracea L. Reveals Their Involvement in Response to Plasmodiophora brassicae Infections

Genome-Wide Identification and Characterization of TCP Family Genes in Pak-Choi [Brassica campestris (syn. Brassica rapa) ssp. chinensis var. communis]