Potato is an important staple food with increasing popularity worldwide. Elevated temperatures significantly impair tuber yield and quality. Breeding heat‐tolerant cultivars is therefore an urgent ...need to ensure sustainable potato production in the future. An integrated approach combining physiology, biochemistry, and molecular biology was undertaken to contribute to a better understanding of heat effects on source‐ (leaves) and sink‐organs (tubers) in a heat‐susceptible cultivar. An experimental set‐up was designed allowing tissue‐specific heat application. Elevated day and night (29°C/27°C) temperatures impaired photosynthesis and assimilate production. Biomass allocation shifted away from tubers towards leaves indicating reduced sink strength of developing tubers. Reduced sink strength of tubers was paralleled by decreased sucrose synthase activity and expression under elevated temperatures. Heat‐mediated inhibition of tuber growth coincided with a decreased expression of the phloem‐mobile tuberization signal SP6A in leaves. SP6A expression and photosynthesis were also affected, when only the belowground space was heated, and leaves were kept under control conditions. By contrast, the negative effects on tuber metabolism were attenuated, when only the shoot was subjected to elevated temperatures. This, together with transcriptional changes discussed, indicated a bidirectional communication between leaves and tubers to adjust the source capacity and/or sink strength to environmental conditions.
Here, we performed a comprehensive study to analyse changes in potato plants under elevated temperatures. A special experimental set‐up allowed us to separately apply temperature stress to either above‐ or belowground tissues and thereby to distinguish between source and sink signals. Our results show that elevated temperatures impair photosynthetic assimilate production and partitioning towards tubers together with a decreased expression of the mobile tuberization signal. Our data led us to conclude that there is a bidirectional signalling between source leaves and sink organs (tubers), and candidate genes are discussed which may be involved in the metabolic readjustment.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Seasonal fluctuations in day length regulate important aspects of plant development such as the flowering transition or, in potato (Solanum tuberosum), the formation of tubers. Day length is sensed ...by the leaves, which produce a mobile signal transported to the shoot apex or underground stems to induce a flowering transition or, respectively, a tuberization transition. Work in Arabidopsis, tomato and rice (Oryza sativa) identified the mobile FLOWERING LOCUS T (FT) protein as a main component of the long-range 'florigen', or flowering hormone, signal. Here we show that expression of the Hd3a gene, the FT orthologue in rice, induces strict short-day potato types to tuberize in long days. Tuber induction is graft transmissible and the Hd3a-GFP protein is detected in the stolons of grafted plants, transport of the fusion protein thus correlating with tuber formation. We provide evidence showing that the potato floral and tuberization transitions are controlled by two different FT-like paralogues (StSP3D and StSP6A) that respond to independent environmental cues, and show that an autorelay mechanism involving CONSTANS modulates expression of the tuberization-control StSP6A gene.
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DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Polyphenols represent a large family of plant secondary metabolites implicated in the prevention of various diseases such as cancers and cardiovascular diseases. The potato is a significant source of ...polyphenols in the human diet. In this study, we examined the expression of thirteen genes involved in the biosynthesis of polyphenols in potato tubers using real-time RT-PCR. A selection of five field grown native Andean cultivars, presenting contrasting polyphenol profiles, was used. Moreover, we investigated the expression of the genes after a drought exposure. We concluded that the diverse polyphenolic profiles are correlated to variations in gene expression profiles. The drought-induced variations of the gene expression was highly cultivar-specific. In the three anthocyanin-containing cultivars, gene expression was coordinated and reflected at the metabolite level supporting a hypothesis that regulation of gene expression plays an essential role in the potato polyphenol production. We proposed that the altered sucrose flux induced by the drought stress is partly responsible for the changes in gene expression. This study provides information on key polyphenol biosynthetic and regulatory genes, which could be useful in the development of potato varieties with enhanced health and nutritional benefits.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Auxin plays a key role during potato tuber development.•The trend of endogenous auxin levels of stolon during potato tuber developmental stages matches with storage root crops.•Emerging literature ...suggest that auxin and related gene regulatory network could regulate storage root development.•Three-way interaction between auxin, SL and mycorrhizal fungi could potentially govern tuber and storage root yield.
Many tuber and storage root crops owing to their high nutritional values offer high potential to overcome food security issues. The lack of information regarding molecular mechanisms that govern belowground storage organ development (except a tuber crop, potato) has limited the application of biotechnological strategies for improving storage crop yield. Phytohormones like gibberellin and cytokinin are known to play a crucial role in governing potato tuber development. Another phytohormone, auxin has been shown to induce tuber initiation and growth, and its crosstalk with gibberellin and strigolactone in a belowground modified stem (stolon) contributes to the overall potato tuber yield. In this review, we describe the crucial role of auxin biology in development of potato tubers. Considering the emerging reports from commercially important storage root crops (sweet potato, cassava, carrot, sugar beet and radish), we propose the function of auxin and related gene regulatory network in storage root development. The pattern of auxin content of stolon during various stages of potato tuber formation appears to be consistent with its level in various developmental stages of storage roots. We have also put-forward the potential of three-way interaction between auxin, strigolactone and mycorrhizal fungi in tuber and storage root development. Overall, we propose that auxin gene regulatory network and its crosstalk with other phytohormones in stolons/roots could govern belowground tuber and storage root development.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Potato (Solanum tuberosum L.) is cultivated worldwide for its underground tubers, which provide an important part of human nutrition and serve as a model system for belowground storage organ ...formation. Similar to flowering, stolon-expressed FLOWERING LOCUS T-like (FT-like) protein SELF-PRUNING 6A (StSP6A) plays an instrumental role in tuberization by binding to the bZIP transcription factors StABI5-like 1 (StABL1) and StFD-like 1 (StFDL1), causing transcriptional reprogramming at the stolon subapical apices. However, the molecular mechanism regulating the widely conserved FT-bZIP interactions remains largely unexplored. Here, we identified a TCP transcription factor StAST1 (StABL1 and StSP6A-associated TCP protein 1) binding to both StSP6A and StABL1. StAST1 is specifically expressed in the vascular tissue of leaves and developing stolons. Silencing of StAST1 leads to accelerated tuberization and a shortened life cycle. Molecular dissection reveals that the interaction of StAST1 with StSP6A and StABL1 attenuates the formation of the alternative tuberigen activation complex (aTAC). We also observed StAST1 directly activates the expression of potato GA 20-oxidase gene (StGA20ox1) to regulate GA responses. These results demonstrate StAST1 functions as a tuberization repressor by regulating plant hormone levels; our findings also suggest a mechanism by which the widely conserved FT-FD genetic module is fine-tuned.
Suberin deposition in potato periderm Tanios, Sabine; Thangavel, Tamilarasan; Eyles, Alieta ...
The New phytologist,
02/2020, Volume:
225, Issue:
3
Journal Article
Peer reviewed
Open access
• Light-induced tuber greening is one of the most important quality defects of potato. Although varietal and maturity factors are known to affect greening resistance, physiological mechanisms of ...resistance are poorly understood. We proposed that physiological and biochemical factors within the tuber periderm provide resistance and hypothesised that resistance is primarily related to suberin content.
• We investigated differences in the tuber periderm between genotypes and tuber maturities that varied in greening propensity. We examined suberin and light-induced pigment accumulation, and phellem cell development and studied greening propensity in mutant and chemically treated tubers with enhanced suberisation.
• Resistance to greening was strongly linked to increased suberin in the periderm, which varied with variety and tuber maturity. Furthermore, greening was reduced in mutant and chemically treated tubers with enhanced suberisation. Increases in phellem cell layers and light-induced carotenoids and anthocyanins were identified as secondary resistance factors.
• Our work represents the first physiological mechanism of varietal and tuber maturity resistance to greening, expanding the known functionality of suberin and providing for the first time a biomarker that will aid producers and breeders in selection and improvement of potato varieties for greening resistance.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Summary
In potato, stolon swelling is a complex and highly regulated process, and much more work is needed to fully understand the underlying mechanisms.
We identified a novel tuber‐specific basic ...helix–loop–helix (bHLH) transcription factor, StbHLH93, based on the high‐resolution transcriptome of potato tuber development.
StbHLH93 is predominantly expressed in the subapical and perimedullary region of the stolon and developing tubers. Knockdown of StbHLH93 significantly decreased tuber number and size, resulting from suppression of stolon swelling. Furthermore, we found that StbHLH93 directly binds to the plastid protein import system gene TIC56 promoter, activates its expression, and is involved in proplastid‐to‐amyloplast development during the stolon‐to‐tuber transition. Knockdown of the target TIC56 gene resulted in similarly problematic amyloplast biogenesis and tuberization.
Taken together, StbHLH93 functions in the differentiation of proplastids to regulate stolon swelling. This study highlights the critical role of proplastid‐to‐amyloplast interconversion during potato tuberization.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Key message
In this study we show that expression of the Arabidopsis
ABF4
gene in potato increases tuber yield under normal and abiotic stress conditions, improves storage capability and processing ...quality of the tubers, and enhances salt and drought tolerance.
Potato is the third most important food crop in the world. Potato plants are susceptible to salinity and drought, which negatively affect crop yield, tuber quality and market value. The development of new varieties with higher yields and increased tolerance to adverse environmental conditions is a main objective in potato breeding. In addition, tubers suffer from undesirable sprouting during storage that leads to major quality losses; therefore, the control of tuber sprouting is of considerable economic importance. ABF (ABRE-binding factor) proteins are bZIP transcription factors that regulate abscisic acid signaling during abiotic stress. ABF proteins also play an important role in the tuberization induction. We developed transgenic potato plants constitutively expressing the Arabidopsis
ABF4
gene (35S::ABF4). In this study, we evaluated the performance of 35S::ABF4 plants grown in soil, determining different parameters related to tuber yield, tuber quality (carbohydrates content and sprouting behavior) and tolerance to salt and drought stress. Besides enhancing salt stress and drought tolerance, constitutive expression of
ABF4
increases tuber yield under normal and stress conditions, enhances storage capability and improves the processing quality of the tubers.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Potatoes usually have the tuber bud end dominance in growth during tuber bulking and in tuber sprouting, likely using carbohydrates from the tuber stem end. We hypothesized that the tuber bud end and ...tuber stem end coordination in carbohydrate metabolism gene expression is different between the bulking dominance and sprouting dominance of the tuber bud end. After comparing the growing tubers at harvest from a green vine and the stage that sprouts just started to emerge after storage of tubers at room temperature, we found the following: (1) Dry matter content was higher in the tuber stem end than the tuber bud end at both stages. (2) The starch granule size was larger in the tuber bud end than in the tuber stem end. (3) The tuber bud end had higher gene expression for starch synthesis but a lower gene expression of sucrose transporters than the tuber stem end during tuber growing. (4) The tuber stem end at the sprouting stage showed more active gene expression in both starch degradation and resynthesis, suggesting more active export of carbohydrates, than the tuber bud end. The results indicate that the starch accumulation mechanism in the tuber bud end was different between field growing and post-harvest sprouting tubers and that tubers already increased dry matter and average starch granule sizes in the tuber bud end prior to the rapid growth of sprouts.
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IJS, KILJ, NUK, PNG, UL, UM, UPUK
Various transcriptional networks and plant hormones have been implicated in controlling different aspects of potato tuber formation. Due to its broad impact on many plant developmental processes, a ...role for auxin in tuber initiation has been suggested but never fully resolved. Here, auxin concentrations were measured throughout the plant prior to and during the process of tuber formation. Auxin levels increase dramatically in the stolon prior to tuberization and remain relatively high during subsequent tuber growth, suggesting a promoting role for auxin in tuber formation. Furthermore, in vitro tuberization experiments showed higher levels of tuber formation from axillary buds of explants where the auxin source (stolon tip) had been removed. This phenotype could be rescued by application of auxin on the ablated stolon tips. In addition, a synthetic strigolactone analogue applied on the basal part of the stolon resulted in fewer tubers. The experiments indicate that a system for the production and directional transport of auxin exists in stolons and acts synergistically with strigolactones to control the outgrowth of the axillary stolon buds, similar to the control of above-ground shoot branching.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
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