Ectopic expression of GhSAMDC1 improved plant vegetative growth and early flowering through conversion of spermidine to spermine in tobacco

Polyamines: pleiotropic molecules regulating plant development and enhancing crop yield and quality

Polyamines (PAs) are pleiotropic bioorganic molecules. Cellular PA contents are determined by a balance between PA synthesis and degradation. PAs have been extensively demonstrated to play vital roles in the modulation of plant developmental processes and adaptation to various environmental stresses. In this review, the latest advances on the diverse roles of PAs in a range of developmental processes, such as morphogenesis, organogenesis, growth and development, and fruit ripening, are summarized and discussed. Besides, the crosstalk between PAs and phytohormones or other signalling molecules, including H2O2 and NO, involved in these processes is dwelled on. In addition, the attempts made to improve the yield and quality of grain and vegetable crops through altering the PA catabolism are enumerated. Finally, several other vital questions that remain unanswered are proposed and discussed. These include the mechanisms underlying the cooperative regulation of developmental processes by PAs and their interplaying partners like phytohormones, H2O2 and NO; PA transport for maintaining homeostasis; and utilization of PA anabolism/catabolism for generating high-yield and good-quality crops. This review aims to gain new insights into the pleiotropic role of PAs in the modulation of plant growth and development, which provides an alternative approach for manipulating and engineering valuable crop varieties that can be used in the future.

Integrated omics approach reveals the molecular pathways activated in tomato by Kocuria rhizophila, a soil plant growth-promoting bacterium

Plant microbial biostimulants application has become a promising and eco-friendly agricultural strategy to improve crop yields, reducing chemical inputs for more sustainable cropping systems. The soil dwelling bacterium Kocuria rhizophila was previously characterized as Plant Growth Promoting Bacteria (PGPB) for its multiple PGP traits, such as indole-3-acetic acid production, phosphate solubilization capability and salt and drought stress tolerance. Here, we evaluated by a multi-omics approach, the PGP activity of K. rhizophila on tomato, revealing the molecular pathways by which it promotes plant growth. Transcriptomic analysis showed several up-regulated genes mainly related to amino acid metabolism, cell wall organization, lipid and secondary metabolism, together with a modulation in the DNA methylation profile, after PGPB inoculation. In agreement, proteins involved in photosynthesis, cell division, and plant growth were highly accumulated by K. rhizophila. Furthermore, "amino acid and peptides", "monosaccharides", and "TCA" classes of metabolites resulted the most affected by PGPB treatment, as well as dopamine, a catecholamine neurotransmitter mediating plant growth through S-adenosylmethionine decarboxylase (SAMDC), a gene enhancing the vegetative growth, up-regulated in tomato by K. rhizophila treatment. Interestingly, eight gene modules well correlated with differentially accumulated proteins (DAPs) and metabolites (DAMs), among which two modules showed the highest correlation with nine proteins, including a nucleoside diphosphate kinase, and cytosolic ascorbate peroxidase, as well as with several amino acids and metabolites involved in TCA cycle. Overall, our findings highlighted that sugars and amino acids, energy regulators, involved in tomato plant growth, were strongly modulated by the K. rhizophila-plant interaction.

Chinese cherry CpMYB44-CpSPDS2 module regulates spermidine content and florescence in tobacco

The flower bud differentiation plays a crucial role in cherry yield and quality. In a preliminary study, we revealed the promotion of spermidine (Spd) in bud differentiation and quality. However, the molecular mechanism underlying Spd regulating cherry bud differentiation remains unclear. To address this research gap, we cloned CpSPDS2, a gene that encodes Spd synthase and is highly expressed in whole flowers and pistils of the Chinese cherry (cv. 'Manaohong'). Furthermore, an overexpression vector with this gene was constructed to transform tobacco plants. The findings demonstrated that transgenic lines exhibited higher Spd content, an earlier flowering time by 6 d, and more lateral buds and flowers than wild-type lines. Additionally, yeast one-hybrid assays and two-luciferase experiments confirmed that the R2R3-MYB transcription factor (CpMYB44) directly binds to and activates the CpSPDS2 promoter transcription. It is indicated that CpMYB44 promotes Spd accumulation via regulating CpSPDS2 expression, thus accelerating the flower growth. This research provides a basis for resolving the molecular mechanism of CpSPDS2 involved in cherry bud differentiation.

A comprehensive overview of cotton genomics, biotechnology and molecular biological studies

Cotton is an irreplaceable economic crop currently domesticated in the human world for its extremely elongated fiber cells specialized in seed epidermis, which makes it of high research and application value. To date, numerous research on cotton has navigated various aspects, from multi-genome assembly, genome editing, mechanism of fiber development, metabolite biosynthesis, and analysis to genetic breeding. Genomic and 3D genomic studies reveal the origin of cotton species and the spatiotemporal asymmetric chromatin structure in fibers. Mature multiple genome editing systems, such as CRISPR/Cas9, Cas12 (Cpf1) and cytidine base editing (CBE), have been widely used in the study of candidate genes affecting fiber development. Based on this, the cotton fiber cell development network has been preliminarily drawn. Among them, the MYB-bHLH-WDR (MBW) transcription factor complex and IAA and BR signaling pathway regulate the initiation; various plant hormones, including ethylene, mediated regulatory network and membrane protein overlap fine-regulate elongation. Multistage transcription factors targeting CesA 4, 7, and 8 specifically dominate the whole process of secondary cell wall thickening. And fluorescently labeled cytoskeletal proteins can observe real-time dynamic changes in fiber development. Furthermore, research on the synthesis of cotton secondary metabolite gossypol, resistance to diseases and insect pests, plant architecture regulation, and seed oil utilization are all conducive to finding more high-quality breeding-related genes and subsequently facilitating the cultivation of better cotton varieties. This review summarizes the paramount research achievements in cotton molecular biology over the last few decades from the above aspects, thereby enabling us to conduct a status review on the current studies of cotton and provide strong theoretical support for the future direction.

Genome-wide evolutionary analysis of AUX/IAA gene family in wheat identifies a novel gene TaIAA15-1A regulating flowering time by interacting with ARF

Flowering time is a critical agronomic trait that has strong effects on crop yields. Auxin signaling pathway plays an important role in various development processes, such as flowering, grain development. However, no Aux/IAA gene had been reported to have functions involving in wheat flowering time. Here, we systematically performed genome-wide identification, classification, domain distribution, exon-intron structure, chromosome locations and global expression pattern of Aux/IAA gene family in 14 plant genomes (including Triticum aestivum). A phylogenetic model was proposed to infer the Aux/IAA evolutionary history involving in a central exon-intron structure "2121" during evolution. Overexpression of TaIAA15-1A caused an early flowering time in Brachypodium. RNA-seq analysis showed that TaIAA15-1A overexpression alters various pathways including phytohormone signaling pathway, flowering-related pathway, and polyamine biosynthesis pathway. Screening of auxin response factor (ARF) genes identified BdARF16 that interacted with TaIAA15-1A. Exogenous polyamine (spermidine and spermine) treatments promoted early flowering and (putrescine and DCHA) delayed flowering time of WT plants. Our finding will provide insights on mechanisms of Aux/IAAs gene family and TaIAA15-1A, illustrating the potential during crop improvement programs.

Improvement of cold tolerance in maize (Zea mays L.) using Agrobacterium-mediated transformation of ZmSAMDC gene

Maize (Zea mays L.) is a food crop sensitive to low temperatures. As one of the abiotic stress hazards, low temperatures seriously affect the yield of maize. However, the genetic basis of low-temperature adaptation in maize is still poorly understood. In this study, maize S-adenosylmethionine decarboxylase (SAMDC) was localized to the nucleus. We used Agrobacterium-mediated transformation technology to introduce the SAMDC gene into an excellent maize inbred line variety GSH9901 and produced a cold-tolerant transgenic maize line. After three years of single-field experiments, the contents of polyamines (PAs), proline (Pro), malondialdehyde (MDA), antioxidant enzymes and ascorbate peroxidases (APXs) in the leaves of the transgenic maize plants overexpressing the SAMDC gene significantly increased, and the expression of elevated CBF and cold-responsive genes effectively increased. The agronomic traits of the maize overexpressing the SAMDC gene changed, and the yield traits significantly improved. However, no significant changes were found in plant height, ear length, and shaft thickness. Therefore, SAMDC enzymes can effectively improve the cold tolerance of maize.

Transcriptome analysis provides insights into the molecular mechanism of GhSAMDC1 involving in rapid vegetative growth and early flowering in tobacco

In previous study, ectopic expression of GhSAMDC₁ improved vegetative growth and early flowering in tobacco, which had been explained through changes of polyamine content, polyamines and flowering relate genes expression. To further disclose the transcript changes of ectopic expression of GhSAMDC₁ in tobacco, the leaves from wild type and two transgenic lines at seedling (30 days old), bolting (60 days old) and flowering (90 days old) stages were performed for transcriptome analysis. Compared to wild type, a total of 938 differentially expressed genes (DEGs) were found to be up- or down-regulated in the two transgenic plants. GO and KEGG analysis revealed that tobacco of wild-type and transgenic lines were controlled by a complex gene network, which regulated multiple metabolic pathways. Phytohormone detection indicate GhSAMDC₁ affect endogenous phytohormone content, ABA and JA content are remarkably increased in transgenic plants. Furthermore, transcript factor analysis indicated 18 transcript factor families, including stress response, development and flowering related transcript factor families, especially AP2-EREBP, WRKY, HSF and Tify are the most over-represented in those transcript factor families. In conclusion, transcriptome analysis provides insights into the molecular mechanism of GhSAMDC₁ involving rapid vegetative growth and early flowering in tobacco.

The multidimensional role of the Wnt/β-catenin signaling pathway in human malignancies

Several signaling pathways have been identified as important for developmental processes. One of such important cascades is the Wnt/β-catenin signaling pathway, which can regulate various physiological processes such as embryonic development, tissue homeostasis, and tissue regeneration; while its dysregulation is implicated in several pathological conditions especially cancers. Interestingly, deregulation of the Wnt/β-catenin pathway has been reported to be closely associated with initiation, progression, metastasis, maintenance of cancer stem cells, and drug resistance in human malignancies. Moreover, several genetic and experimental models support the inhibition of the Wnt/β-catenin pathway to answer the key issues related to cancer development. The present review focuses on different regulators of Wnt pathway and how distinct mutations, deletion, and amplification in these regulators could possibly play an essential role in the development of several cancers such as colorectal, melanoma, breast, lung, and leukemia. Additionally, we also provide insights on diverse classes of inhibitors of the Wnt/β-catenin pathway, which are currently in preclinical and clinical trial against different cancers.