Phytohormones: plant switchers in developmental and growth stages in potato

The molecular coordination of tuberization: Current status and future directions

The integration of bulk transcriptomic, proteomic, and genomic data generated from numerous systems biology studies of tuberizing plants has resulted in a better understanding of the molecular and morphological aspects of tuberization. The identified conserved integrated hormonal, transcriptional, and metabolic pathways of tuberization in crops from various plant lineages support the hypothesis of a fundamental tuberization process. However, further studies are required to specify the additional processes defined by the genomics and phylogeny of the particular plant lineages, which control the morphological diversity of tubers. This review summarizes the latest molecular and morphological discoveries on the tuberization process in stem tubers and tuberous roots and discusses future trajectories of the field.

Tuber quality enhancement via grafting potato onto a wooden goji rootstock through vitalizing multi-pathways

Grafting is applied in Solanaceae to improve growth and quality traits. However, grafting potato onto a wooden goji rootstock is rare. Our study introduces a novel distant grafting technique to investigate potato scion responses, specifically regarding photosynthetic and tuber nutritional quality. The physiological and transcriptomic findings reveal an increase in photosynthesis ratio and carbon fixation in potato leaves after 45 days of grafting due to the upregulation of pivotal genes (PsbA, PPC1, rbcl, and GAPDH). After 95 days of long-term growth, the leaf redox balance was maintained with intensified chlorophyll synthesis, facilitated by the enrichment of crucial genes (GUN4, CHLH, CHLP, CAO) and several light-harvesting proteins (Lhca and Lhcb) in potato leaves. The tubers of grafted plants showed a 6.5% increase in crude protein, 51% in anthocyanin, and lower carbohydrate content. Goji altered the expression of tubers genes involved in assimilatory sulfate reduction, which subsequently affects cysteine-methionine biosynthesis. Furthermore, the tuber transcriptome shows ABA signaling and transcription factors regulate the expression of key biosynthetic genes involved in inducing the secondary metabolites, such as scopoletin and anthocyanin accumulation, which are primary polyphenols in goji. Our innovative grafting approach offers valuable insights into the interactions between woody and herbaceous plants for developing future strategies to modulate growth efficiency and tuber quality in the face of climate challenges and to meet the demand for nutritious food.

Potato: from functional genomics to genetic improvement

Potato is the most widely grown non-grain crop and ranks as the third most significant global food crop following rice and wheat. Despite its long history of cultivation over vast areas, slow breeding progress and environmental stress have led to a scarcity of high-yielding potato varieties. Enhancing the quality and yield of potato tubers remains the ultimate objective of potato breeding. However, conventional breeding has faced challenges due to tetrasomic inheritance, high genomic heterozygosity, and inbreeding depression. Recent advancements in molecular biology and functional genomic studies of potato have provided valuable insights into the regulatory network of physiological processes and facilitated trait improvement. In this review, we present a summary of identified factors and genes governing potato growth and development, along with progress in potato genomics and the adoption of new breeding technologies for improvement. Additionally, we explore the opportunities and challenges in potato improvement, offering insights into future avenues for potato research.

Advances in the Modulation of Potato Tuber Dormancy and Sprouting

The post-harvest phase of potato tuber dormancy and sprouting are essential in determining the economic value. The intricate transition from dormancy to active growth is influenced by multiple factors, including environmental factors, carbohydrate metabolism, and hormonal regulation. Well-established environmental factors such as temperature, humidity, and light play pivotal roles in these processes. However, recent research has expanded our understanding to encompass other novel influences such as magnetic fields, cold plasma treatment, and UV-C irradiation. Hormones like abscisic acid (ABA), gibberellic acid (GA), cytokinins (CK), auxin, and ethylene (ETH) act as crucial messengers, while brassinosteroids (BRs) have emerged as key modulators of potato tuber sprouting. In addition, jasmonates (JAs), strigolactones (SLs), and salicylic acid (SA) also regulate potato dormancy and sprouting. This review article delves into the intricate study of potato dormancy and sprouting, emphasizing the impact of environmental conditions, carbohydrate metabolism, and hormonal regulation. It explores how various environmental factors affect dormancy and sprouting processes. Additionally, it highlights the role of carbohydrates in potato tuber sprouting and the intricate hormonal interplay, particularly the role of BRs. This review underscores the complexity of these interactions and their importance in optimizing potato dormancy and sprouting for agricultural practices.

Mechanism underlying the rapid growth of Phalaenopsis equestris induced by 60Co-γ-ray irradiation

Gamma (γ)-ray irradiation is one of the important modern breeding methods. Gamma-ray irradiation can affect the growth rate and other characteristics of plants. Plant growth rate is crucial for plants. In horticultural crops, the growth rate of plants is closely related to the growth of leaves and flowering time, both of which have important ornamental value. In this study, 60Co-γ-ray was used to treat P. equestris plants. After irradiation, the plant's leaf growth rate increased, and sugar content and antioxidant enzyme activity increased. Therefore, we used RNA-seq technology to analyze the differential gene expression and pathways of control leaves and irradiated leaves. Through transcriptome analysis, we investigated the reasons for the rapid growth of P. equestris leaves after irradiation. In the analysis, genes related to cell wall relaxation and glucose metabolism showed differential expression. In addition, the expression level of genes encoding ROS scavenging enzyme synthesis regulatory genes increased after irradiation. We identified two genes related to P. equestris leaf growth using VIGS technology: PeNGA and PeEXPA10. The expression of PeEXPA10, a gene related to cell wall expansion, was down-regulated, cell wall expansion ability decreased, cell size decreased, and leaf growth rate slowed down. The TCP-NGATHA (NGA) molecular regulatory module plays a crucial role in cell proliferation. When the expression of the PeNGA gene decreases, the leaf growth rate increases, and the number of cells increases. After irradiation, PeNGA and PeEXPA10 affect the growth of P. equestris leaves by influencing cell proliferation and cell expansion, respectively. In addition, many genes in the plant hormone signaling pathway show differential expression after irradiation, indicating the crucial role of plant hormones in plant leaf growth. This provides a theoretical basis for future research on leaf development and biological breeding.

Molecular, in silico and expression studies on lipoxygenases (LOXs) in potato (Solanum tuberosum L.)

Lipoxygenases (LOXs) namely 9-LOXs and 13-LOXs catalyse the oxygenation of polyunsaturated fatty acids to produce fatty acid hydroperoxides which are crucial in growth, development and stress responses in plants. Here, we isolated and characterized a 2723-bp cDNA encoding a distinct 861-aa 9-LOX form, designated StKCLX-1, using tuber total RNA from an Indian potato cultivar, Kufri Chipsona-1 through RT-PCR. A total of 17 LOX genes distributed in different chromosomes were identified and characterized in the potato genome. Multiple sequence alignment revealed highly conserved amino acids in the crucial domains, motifs and variable N-terminal regions between the LOX classes. A total of 36 LOXs from potato, tomato and Arabidopsis were used in phylogenetic analysis. A 3-D structure of StKCLX-1 was predicted by AlphaFold tool, validated through the predicted local-distance difference test (pLDDT) and Ramachandran Plot. Molecular docking predicted the nature of receptor-ligand interactions. STRING database was used to predict the protein-protein interactions. Expression patterns of the LOXs in the potato organs were examined by Expression Atlas and semi-quantitative RT-PCR. 9-LOX activity was noticed at early stages of tuberization, and significantly increased in the freshly-harvested mature tubers. This report would be useful in gaining insights into the structure-function relationships of the LOXs and corresponding multigene family-prerequisites for understanding tuber development in potato.

Real-Time Monitoring of Translocation, Dissipation, and Cumulative Risk of Maleic Hydrazide in Potato Plants and Tubers by Ion Exclusion Chromatography

In this paper, a high-performance ion exclusion chromatographic (ICE) method was developed and applied for monitoring maleic hydrazide (MH) translocation in complex potato plant tissue and tuber matrices. After middle leaf uptake, most MH was trapped and dissipated in the middle leaf, and the rest was transported to other parts mainly through the phloem. Soil absorption significantly reduced the uptake efficiency of the root system, in which MH was partitioned to dissipate in root protoplasts or transfer through the xylem and persisted in the plant. Tuber uptake enabled MH to remain in the flesh and maintain stable levels under storage conditions, but during germination, MH was translocated from the flesh to the growing buds, where it dissipated through the short-day photoperiodic regime. The results demonstrated successful application of the ICE method and provided necessary insights for real-time monitoring of MH translocation behavior to effectively improve potato edible safety.

Study on Potato Bud Cultivation Techniques in a Greenhouse in Spring

The species degeneration caused by traditional potato cultivation methods is becoming increasingly evident, and it is particularly important to study new potato cultivation methods. Sprout planting technology has the advantages of large reproductive capacity, fast growth speed, and simplified maintenance of cultivated crops. In this study, four disease-free potato varieties ('Fujin', 'Youjin', 'Zhongshu 4', and 'Feiwuruita') were treated with different parts (top bud, middle bud, and tail bud) and different bud lengths (10 cm, 15 cm, and 20 cm), and then potato sprout planting was carried out. A nutrient pot experiment was performed following a randomized complete block design (RCBD) with various replicates and a natural control (CK) treatment. By comprehensively measuring the emergence, chlorophyll content, net photosynthetic rate, dry matter distribution during the bulking period of blocks, and effect of growth and quality with bud direct seeding under both treatments, it was found that potato block top bud direct seeding cultivation is significantly superior to other parts. In terms of early maturity and yield statistics, the advantage of top bud cultivation in 'zhongshu 4' is most obvious; it reaches maturity an average of 14 days earlier, and the yield can be increased by 38.05%. Therefore, top bud direct seeding is more suitable for potato sprout planting technology. On this basis, the 20 cm and 15 cm bud length treatments of top buds were used for direct cultivation, and all the above indicators performed well. Among them, in the zhongshu 4 variety, the yields of 15 cm and 20 cm bud length treatments increased by 41.78% and 38.05%, the growth rates of commercial potatoes increased by 6% and 6.9%, respectively, and the effects were the most obvious. In conclusion, the deep research and application of potato sprouting technology has high utilization value for improving potato yield and quality and has guiding significance for greenhouse potato cultivation in early spring.

The Retinoblastoma-related gene RBL901 can trigger drought response actions in potato

KEY MESSAGE

This study provided new insights into response of potato to drought stress.

Combined analysis of the transcriptome and metabolome provides insights into the fleshy stem expansion mechanism in stem lettuce

As a stem variety of lettuce, the fleshy stem is the main product organ of stem lettuce. The molecular mechanism of fleshy stem expansion in stem lettuce is a complex biological process. In the study, the material accumulation, gene expression, and morphogenesis during fleshy stem expansion process were analyzed by the comparative analysis of metabolome, transcriptome and the anatomical studies. The anatomical studies showed that the occurrence and activity of vascular cambium mainly led to the development of fleshy stems; and the volume of pith cells gradually increased and arranged tightly during the expansion process. A total of 822 differential metabolites and 9,383 differentially expressed genes (DEGs) were identified by the metabolomics and transcriptomics analyses, respectively. These changes significantly enriched in sugar synthesis, glycolysis, and plant hormone anabolism. The expression profiles of genes in the sugar metabolic pathway gradually increased in fleshy stem expansion process. But the sucrose content was the highest in the early stage of fleshy stem expansion, other sugars such as fructose and glucose content increased during fleshy stem expansion process. Plant hormones, including IAA, GA, CTK, and JA, depicted important roles at different stem expansion stages. A total of 1,805 DEGs were identified as transcription factors, such as MYB, bHLH, and bZIP, indicating that these transcription factor families might regulate the fleshy stems expansion in lettuce. In addition, the expression patterns identified by qRT-PCR were consistent with the expression abundance identified by the transcriptome data. The important genes and metabolites identified in the lettuce fleshy stem expansion process will provide important information for the further molecular mechanism study of lettuce fleshy stem growth and development.

Transcriptomic analysis of succulent stem development of Chinese kale (Brassica oleracea var. alboglabra Bailey) and its synthetic allotetraploid via RNA sequencing

Chinese kale (Brassica oleracea var. alboglabra Bailey, CC) is a succulent stem vegetable in the Brassica family. Its allotetraploid (AACC) vegetable germplasm, which was synthesized via distant hybridization with the colloquially named 'yellow turnip' (B. rapa L. ssp. rapifera Matzg., AA), has a swelling stem similar to CC. To address the molecular mechanism of stem development for CC and AACC, RNA sequencing (RNA-seq) was used to investigate transcriptional regulation of their stem development at three key stages including 28 days, 42 days and the bolting stage (BS) after sowing. As a result, 32,642, 32,665, 33,816, 32,147, 32,293 and 32,275 genes were identified in six corresponding cDNA libraries. Among them, 25,459 genes were co-expressed, while 7,183, 7,206, 8,357, 6,688, 6,834 and 6,814 genes were specifically expressed. Additionally, a total of 29,222 differentially expressed genes (DEGs) were found for functional enrichment as well as many genes involved in plant hormones including gibberellin (GA), abscisic acid (ABA), cytokinin (CTK) and auxin (AUX). Based on gene expression consistency between CC and AACC, the gene families including DELLA, GID, PYR/PYL, PP2C, A-ARR and AUX/IAA might be related to stem development. Among these, eight genes including Bo00834s040, Bo5g093140, Bo6g086770, Bo9g070200, Bo7g116570, Bo3g054410, Bo7g093470 and Bo5g136600 may play important roles in stem development based on their remarkable expression levels as confirmed by qRT-PCR. These findings provide a new theoretical basis for understanding the molecular mechanism of stem development in Brassica vegetable stem breeding.

The carbohydrate elicitor Riclinoctaose facilitates defense and growth of potato roots by inducing changes in transcriptional and metabolic profiles

Promoting both root growth and defense is conducive to the production of potatoes (Solanum tuberosum L.), while the role of elicitors in this topic hasn't been fully understood. To investigate the effect of Riclinoctaose (RiOc) on root growth and defense, potato tissue cuttings were cultivated with different concentration of RiOc (0, 50, 200 mg/L) for 5 weeks and changes in root morphology, transcription, enzymatic and metabolomic profiles were monitored over time. The results indicated that RiOc triggered the salicylic acid (SA)-mediated defense response and facilitated the growth of adventitious and lateral roots in a dose- and time-dependent manner. MPK3/MPK6, SA- and auxin-signaling pathways and transcription factors such as WUS, SCR and GRAS4/GRAS9 participated in this process. Moreover, the ¹H NMR based metabolome profiling demonstrated that potato roots altered the primary metabolism to respond to the RiOc elicitation and efficiency in production and allocation of defense and growth-related metabolites was improved. After 5-week treatment, the level of glucose, N-acetylglucosamine, glutamine, asparagine, isoleucine, valine, 3-hydroxyisovalerate and ferulate increased, while acetate, acetoacetate, fucose, and 2-hydroxyphenylacetate declined. In conclusion, RiOc played dual roles in activating the SA-mediated defense response and in promoting growth of potato roots by inducing changes in root transcription and metabolism.

Senescence-associated proteins and nitrogen remobilization in grain filling under drought stress condition

Background

Plants use escape strategies including premature senescence and leaf reduction to cope in response to drought stress, which in turn reduces plant leaves and photosynthesis. This strategy allows the new generation (seeds) to survive under drought but, plants experience more yield loss during stress condition. The amount of damage caused by drought stress is compensated by the expression of genes involved in regulating leaf aging. Leaf senescence alters the expression of thousands of genes and ultimately affecting grain protein content, grain yield, and nitrogen utilization efficiency. Also, under drought stress, nitrogen in the soil will not become as much available and causes the beginning and acceleration of the senescence process of leaves.

The main body of the abstract

This review identified proteins signaling and functional proteins involved in senescence. Further, transcription factors and cell wall degradation enzymes (proteases) related to senescence during drought stress were surveyed. We discuss the regulatory pathways of genes as a result of the degradation of proteins during senescence process. Senescence is strongly influenced by plant hormones and environmental factors including the availability of nitrogen. During maturity or drought stress, reduced nitrogen uptake can cause nitrogen to be remobilized from leaves and stems to seeds, eventually leading to leaf senescence. Under these conditions, genes involved in chloroplast degradation and proteases show increased expression. The functional (proteases) and regulatory proteins such as protein kinases and phosphatases as well as transcription factors (AP2/ERF, NAC, WRKY, MYB, and bZIP) are involved in leaf senescence and drought stress.

Short conclusion

In this review, senescence-associated proteins involved in leaf senescence and regulatory and functional proteins in response to drought stress during grain filling were surveyed. The present study predicts on the role of nitrogen transporters, transcription factors and regulatory genes involved in the late stages of plant growth with the aim of understanding their mechanisms of action during grain filling stage. For a better understanding, the relevant evidence for the balance between grain filling and protein breakdown during grain filling in cereals is presented.

The application of plant growth-promoting rhizobacteria in Solanum lycopersicum production in the agricultural system: a review

Food safety is a significant challenge worldwide, from plantation to cultivation, especially for perishable products such as tomatoes. New eco-friendly strategies are needed, and beneficial microorganisms might be a sustainable solution. This study demonstrates bacteria activity in the tomato plant rhizosphere. Further, it investigates the rhizobacteria's structure, function, and diversity in soil. Rhizobacteria that promote the growth and development of tomato plants are referred to as plant growth-promoting bacteria (PGPR). They form a series of associations with plants and other organisms in the soil through a mutualistic relationship where both parties benefit from living together. It implies the antagonistic activities of the rhizobacteria to deter pathogens from invading tomato plants through their roots. Some PGPR are regarded as biological control agents that hinder the development of spoilage organisms and can act as an alternative for agricultural chemicals that may be detrimental to the health of humans, animals, and some of the beneficial microbes in the rhizosphere soil. These bacteria also help tomato plants acquire essential nutrients like potassium (K), magnesium (Mg), phosphorus (P), and nitrogen (N). Some rhizobacteria may offer a solution to low tomato production and help tackle food insecurity and farming problems. In this review, an overview of soil-inhabiting rhizobacteria focused on improving the sustainable production of Solanum lycopersicum.

Roles of Abscisic Acid and Gibberellins in Stem/Root Tuber Development

Root and tuber crops are of great importance. They not only contribute to feeding the population but also provide raw material for medicine and small-scale industries. The yield of the root and tuber crops is subject to the development of stem/root tubers, which involves the initiation, expansion, and maturation of storage organs. The formation of the storage organ is a highly intricate process, regulated by multiple phytohormones. Gibberellins (GAs) and abscisic acid (ABA), as antagonists, are essential regulators during stem/root tuber development. This review summarizes the current knowledge of the roles of GA and ABA during stem/root tuber development in various tuber crops.

Hormonal Regulation and Crosstalk of Auxin/Cytokinin Signaling Pathways in Potatoes In Vitro and in Relation to Vegetation or Tuberization Stages

Auxins and cytokinins create versatile regulatory network controlling virtually all aspects of plant growth and development. These hormonal systems act in close contact, synergistically or antagonistically, determining plant phenotype, resistance and productivity. However, the current knowledge about molecular interactions of these systems is still scarce. Our study with potato plants aimed at deciphering potential interactions between auxin and cytokinin signaling pathways at the level of respective gene expression. Potato plants grown on sterile medium with 1.5% (vegetation) or 5% (tuberization) sucrose were treated for 1 h with auxin or cytokinin. Effects of these two hormones on expression profiles of genes belonging to main signaling pathways of auxin and cytokinin were quantified by RT-qPCR. As a result, several signaling genes were found to respond to auxin and/or cytokinin by up- or down-regulation. The observed effects were largely organ-specific and depended on sucrose content. Auxin strongly reduced cytokinin perception apparatus while reciprocal cytokinin effect was ambiguous and sucrose-dependent. In many cases, functional clustering of genes of the same family was observed. Promoters in some clusters are enriched with canonic hormone-response cis-elements supporting their direct sensitivity to hormones. Collectively, our data shed new light on the crosstalk between auxin- and cytokinin signaling pathways.