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Shoot branching is an important aspect of plant architecture because it substantially affects plant biology and agricultural performance. Sugars play an important role in the induction of shoot branching in several species, including potato (Solanum tuberosum L.). However, the mechanism by which sugars affect shoot branching remains mostly unknown. In the present study, we addressed this question using sugar-mediated induction of bud outgrowth in potato stems under etiolated conditions. Our results indicate that sucrose feeding to detached stems promotes the accumulation of cytokinin (CK), as well as the expression of vacuolar invertase (VInv), an enzyme that contributes to sugar sink strength. These effects of sucrose were suppressed by CK synthesis and perception inhibitors, while CK supplied to detached stems induced bud outgrowth and VInv activity in the absence of sucrose. CK-induced bud outgrowth was suppressed in vinv mutants, which we generated by genome editing. Altogether, our results identify a branching-promoting module, and suggest that sugar-induced lateral bud outgrowth is in part promoted by the induction of CK-mediated VInv activity. [ABSTRACT FROM AUTHOR]

The potato (Solanum tuberosum) tuber is a swollen stem. Sprouts growing from the tuber nodes represent loss of apical dominance and branching. Long cold storage induces loss of tuber apical dominance and results in secondary branching. Here, we show that a similar branching pattern can be induced by short heat treatment of the tubers. Detached sprouts were induced to branch by the heat treatment only when attached to a parenchyma cylinder. Grafting experiments showed that the scion branches only when grafted onto heat- or cold-treated tuber parenchyma, suggesting that the branching signal is transmitted systemically from the bud-base parenchyma to the grafted stem. Exogenous supply of sucrose (Suc), glucose, or fructose solution to detached sprouts induced branching in a dose-responsive manner, and an increase in Suc level was observed in tuber parenchyma upon branching induction, suggesting a role for elevated parenchyma sugars in the regulation of branching. However, sugar analysis of the apex and node after grafting showed no distinct differences in sugar levels between branching and nonbranching stems. Vacuolar invertase is a key enzyme in determining the level of Suc and its cleavage products, glucose and fructose, in potato parenchyma. Silencing of the vacuolar invertase-encoding gene led to increased tuber branching in combination with branching-inducing treatments. These results suggest that Suc in the parenchyma induces branching through signaling and not by excess mobilization from the parenchyma to the stem. [ABSTRACT FROM AUTHOR]

Endodormancy (ED) is a crucial stage in the life cycle of many perennial plants. ED release requires accumulating a certain amount of cold exposure, measured as chilling units. However, the mechanism governing the effect of chilling on ED duration is poorly understood. We used the potato tuber model to investigate the response to chilling as associated with ED release. We measured the accumulation of specific sugars during and after chilling, defined as sugar units. We discovered that ED duration correlated better with sugar units accumulation than chilling units. A logistic function was developed based on sugar units measurements to predict ED duration. Knockout or overexpression of the vacuolar invertase gene (StVInv) unexpectedly modified sugar units levels and extended or shortened ED, respectively. Silencing the energy sensor SNF1‐related protein kinase 1, induced higher sugar units accumulation and shorter ED. Sugar units accumulation induced by chilling or transgenic lines reduced plasmodesmal (PD) closure in the dormant bud meristem. Chilling or knockout of abscisic acid (ABA) 8′‐hydroxylase induced ABA accumulation, in parallel to sweetening, and antagonistically promoted PD closure. Our results suggest that chilling induce sugar units and ABA accumulation, resulting in antagonistic signals for symplastic connection of the dormant bud. Summary statement: Endodormancy (ED) duration of potato tuber correlates better with soluble sugars accumulation (sugar units) than chilling units. Chilling induces sugar units and ABA accumulation, resulting in antagonistic signals for symplastic connection of the dormant bud, determining ED duration. [ABSTRACT FROM AUTHOR]

During nonventilated storage of carrots, CO2 gradually accumulates to high levels and causes modifications in the carrot's microbiome toward dominance of Lactobacillales and Enterobacteriales. The lactic acid bacterium Leuconostoc mesenteroides secretes a slimy exudate over the surface of the carrots. The objective of this study was to characterize the slime components and the potential cause for its secretion under high CO2 levels. A proteomic analysis of the exudate revealed bacterial glucosyltransferases as the main proteins, specifically, dextransucrase. A chemical analysis of the exudate revealed high levels of dextran and several simple sugars. The exudate volume and dextran amount were significantly higher when L. mesenteroides was incubated under high CO2 levels than when incubated in an aerated environment. The treatment of carrot medium plates with commercial dextransucrase or exudate protein extract resulted in similar sugar profiles and dextran production. Transcriptome analysis demonstrated that dextran production is related to the upregulation of the L. mesenteroides dextransucrase-encoding genes dsrD and dsrT during the first 4 to 8-h of exposure to high CO2 levels compared to aerated conditions. A phylogenetic analysis of L. mesenteroides YL48 dsrD revealed a high similarity to other dsr genes harbored by different Leuconostoc species. The ecological benefit of dextran production under elevated CO2 requires further investigation. However, this study implies an overlooked role of CO2 in the physiology and fitness of L. mesenteroides in stored carrots, and perhaps in other food items, during storage under nonventilated conditions. IMPORTANCE The bacterium Leuconostoc mesenteroides is known to cause spoilage of different types of foods by secreting a slimy fluid that damages the quality and appearance of the produce. Here, we identified a potential mechanism by which high levels of CO2 affect the spoilage caused by this bacterium by upregulating dextran synthesis genes. These results have broader implications for the study of the physiology, degradation ability, and potential biotechnological applications of Leuconostoc. [ABSTRACT FROM AUTHOR]

The potato tuber is a swollen stem, which is used as the propagation material for commercial potato crops. At the end of a period of dormancy, the number of sprouts growing from the tuber nodes represent loss of tuber apical dominance (AD) resulting in branching. In Mediterranean countries, seed tubers cannot be kept in cold storage for a long period as it leads to over-branching of the seed tuber after replanting. In order to test the hypothesis that temperature exposure in the field effects dormancy length and/or AD postharvest, we exposed seed tubers to different numbers of growing-degree days (GDD) during their development. Seed tubers were cultivated at 0, 300 and 880 m above sea level (ASL), at three different planting dates. Crops were exposed to 780–1250 GDD and extended growth period induce linear accumulating GDD. For both cultivars, ‘Desiree’ and ‘Nicola’, there was a low correlation between GDD in the field and the number of days of storage at 2 °C before 70% of the tubers were released from dormancy. The main factor affecting the duration of dormancy period was the cultivar. In both cultivars, there was a low correlation between the seed-tuber crop’s exposure to GDD and the number of stems that emerged from the replanted tubers. The number of produced stems was mainly affected by the length of the storage period until replanting. Tubers that were replanted in the fall (following 130–190 d of storage) produced two to four stems each; whereas tubers replanted in the spring (following 210–270 d of storage) produced four to seven stems. There was a low correlation between mother-plant exposure to GDD in the field and total yield of the daughter plants. In both cultivars, exposure of the mother plants to different numbers of GDD did not have any significant effect on the size distribution of the tubers produced by the daughter plants. Extending the storage period did consistently induce yield of smaller sized tubers. We suggest that potato seed-tubers do not “remember” their GDD history and their AD is mainly affected by the duration of cold storage. [ABSTRACT FROM AUTHOR]

A simple method for the synthesis of nanoparticles (NPs) of silver (Ag) in a matrix of bovine submaxillary mucin (BSM) was reported previously by some of the authors of this study. Based on mucin characteristics such as long-lasting stability, water solubility, and surfactant and adhesive characteristics, we hypothesized that these compounds, named BSM-Ag NPs, may possess favorable properties as potent antimicrobial agents. The goal of this study was to assess whether BSM-Ag NPs possess antibacterial activity, focusing on important plant-pathogenic bacterial strains representing both Gram-negative (Acidovorax and Xanthomonas) and Grampositive (Clavibacter) genera. Growth inhibition and bactericidal assays, as well as electron microscopic observations, demonstrate that BSM-Ag NPs, at relatively low concentrations of silver, exert strong antimicrobial effects. Moreover, we show that treatment of melon seeds with BSM-Ag NPs effectively prevents seed-to-seedling transmission of Acidovorax citrulli, one of the most threatening pathogens of cucurbit production worldwide. Overall, our findings demonstrate strong antimicrobial activity of BSM-Ag NPs and their potential application for reducing the spread and establishment of devastating bacterial plant diseases in agriculture. [ABSTRACT FROM AUTHOR]

Garlic is a sterile plant that reproduces vegetatively through cloves. We previously found that in ‘Shani’, a garlic cultivar adapted to Mediterranean climate, preplanting storage temperature alters plant development, architecture and yield during the growing period. To determine the possible mechanism underlying this phenomenon, the effects of two temperature treatments, 2 °C and 33 °C, were examined in the internal bud (IB) and storage leaf (SL) of garlic cloves using a transcriptomic approach. Higher representation of carbohydrate metabolism genes was found in cloves at 2 °C vs. 33 °C in both analyzed organs. Of the upregulated genes, 34% were common to IB and SL, whereas 15% and 51%, respectively, were organ-specific. Gene-ontology analysis confirmed that in both organs, carbohydrate metabolism-related genes are more highly expressed at 2 °C than at 33 °C. Chromatography analysis of fructan-degradation products sucrose and fructose in the IB and SL confirmed their higher availability at 2 °C vs. 33 °C. Expression analysis of garlic homologs of meristem-specific and flowering genes revealed differential expression patterns at 2 °C vs. 33 °C. RNA-Seq data were validated by real-time quantitative PCR of 10 candidate genes related to carbohydrate metabolism and flowering; results suggested that FLOWERING LOCUS T2 ( FT2 ) is affected by carbohydrate metabolism. Overexpression of garlic FT2 in Arabidopsis resulted in an early-flowering phenotype and early termination of stem development. We suggest that preplanting environment temperature alters carbohydrate metabolism and consequently FT2 expression, affecting the timing of meristem termination and bulbing after replanting the garlic clove. [ABSTRACT FROM AUTHOR]

• Postharvest heat treatment stimulates desiccation of outer scales of onion. • Inner scales resist the heat treatment and showed increasing soluble sugar levels. • Exogenous feeding of outer scales with sugars solutions reduced water loss. • Transcriptomics suggest differential response to heat of outer vs. inner scales. Postharvest heat treatment stimulates desiccation and browning of outer scales of onion (Allium cepa. L) bulb to dry papery skins. Inner scales resist the heat treatment, as evidenced by high moisture levels. During heating, inner scales showed increasing soluble sugar levels followed by higher osmolarity, vs. a dramatic decrease in both in the outer scales. Exogenous feeding of outer scales with sucrose, glucose or fructose solutions before heat treatment reduced water loss during heating, suggesting a role for soluble sugars in water retention and therefore, heat tolerance. Vacuolar invertase (VInv) is a key enzyme regulating the levels of sucrose, glucose and fructose in plant tissue. In onion outer scales, VInv activity increased during heating but reducing sugars decreased, possibly due to their rapid metabolism during scale senescence to form skin. Transcriptomic analysis demonstrated upregulation of genes involved in lignin biosynthesis and secondary cell-wall formation in outer scales during heat exposure, and upregulation of genes involved in energy-related pathways in inner scales. This study reveals the dual role of soluble sugars in different onion scales, as osmoprotectants or building blocks, under heat stress. [ABSTRACT FROM AUTHOR]