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Dormancy and reducing sugar content in tubers are important traits of potato and are typical quantitative traits. Deciphering the genetic basis of potato tuber dormancy and reducing sugar content is a prerequisite for improving the two traits. DorB5.3, a stable major dormancy QTL (quantitative trait locus) previously mapped across seven environments, has been found to co-localize with RECB05-1, a QTL controlling reducing sugar content in potato tubers. In order to determine whether DorB5.3 was a pleiotropic QTL or not, a conditional QTL mapping was carried out, and the results suggested that DorB5.3 and RECB05-1 were the same QTL, controlling the dormancy and reducing sugar content in potato tubers simultaneously. Conditional QTL mapping also uncovered three pairs of epistatic QTLs which were independent of the reducing sugar content and were significant for deciphering the genetic basis of dormancy. Five genes were picked out as putative causal genes controlling DorB5.3, according to the genome annotation and transcriptomic data. The pleiotropic DorB5.3 along with the negative correlation between the causal and resultant traits provided a possibility that potato breeders could prolong the dormancy period and scale back the reducing sugar content of potato tubers in one breeding program. The results of this study could pave a way for understanding the genetic basis of both dormancy and reducing sugar content in potato breeding programs. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) is critical in drought tolerance and plant growth. Group A protein type 2C phosphatases (PP2Cs) are negative regulators of ABA signaling and plant adaptation to stress. Knowledge about the functions of potato group A PP2Cs is limited. Here, we report that the potato group A PP2C StHAB1 is broadly expressed in potato plants and strongly induced by ABA and drought. Suppression of StHAB1 enhanced potato ABA sensitivity and drought tolerance, whereas overexpression of the dominant mutant StHAB1 G276D compromised ABA sensitivity and drought tolerance. StHAB1 interacts with almost all ABA receptors and the Snf1-Related Kinase OST1. Suppressing StHAB1 and overexpressing StHAB1 G276D alter potato growth morphology; notably, overexpression of StHAB1 G276D causes excessive shoot branching. RNA-sequencing analyses identified that the auxin efflux carrier genes StPIN3 , StPIN5 , and StPIN8 were up-regulated in StHAB1 G276D -overexpressing axillary buds. Correspondingly, the auxin concentration was reduced in StHAB1 G276D -overexpressing axillary buds, consistent with the role of auxin in repressing lateral branch outgrowth. The expression of BRANCHED1 s (StBRC1a and StBRC1b) was unchanged in StHAB1 G276D -overexpressing axillary buds, suggesting that StHAB1 G276D overexpression does not cause axillary bud outgrowth via regulation of BRC1 expression. Our findings demonstrate that StHAB1 is vital in potato drought tolerance and shoot branching. [ABSTRACT FROM AUTHOR]

CRISPR-Cas systems endow the bacterial and archaeal species with adaptive immune mechanisms to fend off invading phages and foreign plasmids. The class 2 type VI CRISPR/Cas effector Cas13d has been harnessed to confer the protection against RNA viruses in diverse eukaryotic species. However a vast number of different viruses can potentially infect the same host plant resulting in mixed infection, thus necessitating the generation of crops with broad-spectrum resistance to multiple viruses. Here we report the repurposing of CRISPR/Cas13d coupled with an endogenous tRNA-processing system (polycistronic tRNA-gRNA, PTG) to target the multiple potato RNA viruses. Expression of Cas13d and four different gRNAs were observed in transgenic potato lines expressing the Cas13d/PTG construct. We show that the Cas13d/PTG transgenic plants exhibit resistance to either PVY, PVS, PVX or PLRV alone or two/three viruses simultaneously by reducing viral accumulation in plant cells. In sum, our findings provide an efficient strategy for engineering crops that can simultaneously resist infection by multiple RNA viruses. CRISPR/Cas13d coupled with an endogenous tRNA-processing system can be used to engineer resistance to multiple RNA viruses in potato. [ABSTRACT FROM AUTHOR]

HSP40 (also known as DnaJ), HSP70, and HSP90 are major heat shock protein (HSP) families that play critical roles in plant growth and development and stress adaption. Recently, several members of the three HSP families were reported to be widely involved in the plant host-virus interactions. However, their global expression profiles and core members recruited by viruses are largely unknown. In this study, a total of 89 StDnaJs were identified from a genome-wide survey, and their classification, phylogenetic relationships, chromosomal locations, and gene duplication events were further analyzed. Together with 20 StHSP70s and 7 StHSP90s previously identified in the potato genome, the global expression patterns of the members in 3 HSP families were investigated in 2 potato cultivars during Potato virus Y (PVY) infection using RNA-seq data. Of them, 16 genes (including 8 StDnaJs, 6 StHSP70s, and 2 StHSP90s) were significantly up- or downregulated. Further analysis using qRT-PCR demonstrated that 7 of the 16 genes (StDnaJ06, StDnaJ17, StDnaJ21, StDnaJ63, StHSP70-6, StHSP70-19, and StHSP90.5) were remarkably upregulated in the potato cultivar 'Eshu 3' after PVY infection, implying their potential roles in the potato-PVY compatible interaction. Subsequent virus-induced gene silencing (VIGS) assays showed that silencing of the homologous genes of StDnaJ17, StDnaJ21, StHSP70-6, and StHSP90.5 in Nicotiana. benthamiana plants dramatically reduced the accumulation of PVY, which indicated the four genes may function as susceptibility factors in PVY infection. This study provides candidate genes for exploring the mechanism of potato-PVY compatible interaction and benefits breeding work aiming to produce new cultivars with the ability to grow healthily under PVY infection. [ABSTRACT FROM AUTHOR]

Summary: CRISPR/Cas systems provide bacteria and archaea with molecular immunity against invading phages and foreign plasmids. The class 2 type VI CRISPR/Cas effector Cas13a is an RNA‐targeting CRISPR effector that provides protection against RNA phages. Here we report the repurposing of CRISPR/Cas13a to protect potato plants from a eukaryotic virus, Potato virus Y (PVY). Transgenic potato lines expressing Cas13a/sgRNA (small guide RNA) constructs showed suppressed PVY accumulation and disease symptoms. The levels of viral resistance correlated with the expression levels of the Cas13a/sgRNA construct in the plants. Our data further demonstrate that appropriately designed sgRNAs can specifically interfere with multiple PVY strains, while having no effect on unrelated viruses such as PVA or Potato virus S. Our findings provide a novel and highly efficient strategy for engineering crops with resistances to viral diseases. [ABSTRACT FROM AUTHOR]

Potato cultivar Exploits and breeding clone F87084 have been considered resistant to Potato virus Y (PVY). To further explore the degree of resistance and whether the resistance is strain specific, these materials, together with cultivar Rochdale Gold-Dorée and breeding line F02010, were investigated for their response to different PVY strains including PVY, PVY, PVY and PVY. Both F02010 and Rochdale Gold-Dorée were readily infected with all tested PVY strains after either mechanical or graft inoculation, indicating susceptibility of the materials to PVY. F87084 was unable to be infected by any of the tested PVY strains as no ELISA-detectable level of PVY were found in plants after either mechanical or graft inoculation, demonstrating extreme resistance in F87084 to all strains of PVY tested. Exploits was infected with PVY/PVY/PVY after either mechanical or graft inoculation, indicating susceptibility of the cultivar to these PVY strains. The cultivar was also infected readily with PVY after graft inoculation. However, despite induction of local lesions on the inoculated leaves, mechanical inoculation with PVY may or may not lead to systemic symptoms and ELISA-detectable level of PVY, depending on temperature. At low temperature (e.g., 22 °C), no visible systemic symptoms or ELISA-detectable level of PVY was found in the plants; whereas at high temperature (e.g., 30 °C), systemic symptoms and high level of PVY were detected in the plants. These results demonstrate that Exploits possesses temperature-dependent hypersensitive resistance to PVY. Analysis of a segregating population of F87084 × F02010 revealed that the ER in F87084 is controlled by a dominant resistance gene. [ABSTRACT FROM AUTHOR]

The responses of 14 potato cultivars to five Potato virus Y (PVY) isolates belonging to four strains (ordinary [PVYO], tobacco veinal necrosis [PVYN], N:O group [PVYN:O], and nonrecombinant potato tuber necrotic [PVYNTN]) were studied in primary and secondary infections. For the primary infection experiments, foliage symptoms were monitored daily after mechanical inoculation with a PVY isolate until harvest; and, for the secondary infection experiments, foliage symptoms were monitored regularly from plant emergence until harvest. Tuber symptoms (namely, tuber necrotic ringspots) were checked at harvest and monthly postharvest for up to 4 months. In both infections, symptoms varied significantly depending on potato cultivar and virus strain or isolate. In primary infections, local lesions occurred on inoculated leaves of 'AC Chaleur', 'Eramosa', 'Goldrush', 'Jemseg', 'Katahdin', 'Ranger Russet', and 'Yukon Gold' after inoculation with PVYO isolates, followed by systemic necrosis on latterly emerged uninoculated leaves. In contrast, plants of 'CalWhite', 'La Rouge','Red LaSoda', 'Russet Burbank', 'Russet Norkotah', and 'Superior' did not exhibit any visible symptoms on inoculated leaves but developed mild to severe mosaic on latterly emerged leaves after infection with PVYO] isolates. In all cultivars, near-symptomless to mild mosaic was induced by PVYN and mild to severe mosaic by [PVYN:O]. [PVYNTN] induced mild to severe mosaic in plants of all cultivars except AC Chaleur, 'Cherokee', and Yukon Gold, which developed visible systemic necrosis. Necrotic ringspots were observed in tubers of PVYNTN-infected plants of AC Chaleur, Cherokee, and Yukon Gold. The tuber symptoms were also incited by PVYN-Jg on Cherokee. In secondary infections, the symptoms were generally more severe than primary infections even though the symptom types did not alter. As in the greenhouse, a clear symptom severity pattern (PVYO -FL > PVYO-RB > PVYNTN-SI > PVYN:O-Mb58 > PVYN-Jg) was observed in AC Chaleur, Cherokee, Eramosa, Goldrush, Jemseg, Katahdin. Ranger Russet, and Yukon Gold in the field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low N level extended tuber dormancy and sales period for commercial potatoes. • Appropriate N level shortened the dormancy and increased the yield of seed tubers. • N application delayed the development of stolons into tubers. • Tuber dormancy regulation by N application is closely related to tuber development. • Sucrose and gibberellins mediate N regulation of tuberization and sprouting. Regulation of tuber dormancy and sprouting are pivotal for postharvest storage, sales, and seed breeding of potatoes (Solanum tuberosum L.). Nitrogen is an essential mineral nutrient required in potato production, which directly influences tuber development and quality. However, the effects of nitrogen on the post-harvest dormancy of potato tubers remain unclear, and their association with the initial tuber development are poorly understood. The aim of this study was to clarify the effects of nitrogen application rate on potato tuber dormancy and the associated physiological mechanisms. We obtained the tubers of different commercial potato cultivars (E shu3, Z shu5, and H shu3) at three nitrogen levels (0, 210, and 315 kg N ha−1) through field experiment, and then stored the tubers at room temperature (25 ℃) in the dark for 0–16 weeks. The dormancy period and alkaloid accumulation of potato tubers were analyzed, and the quality of seed tubers was evaluated by examining eye sprouting and replanting. We also conducted a pot experiment to explore the differences in tuber and stolen development of one potato cultivar (H shu3) at the three nitrogen levels. The carbohydrate and phytohormone contents in the apical bud meristem of dormant tubers and the enlarged subapical region of stolons were measured. The results showed that a reduction in the nitrogen application rate extended the dormancy period of potato tubers by 3–6 weeks and thereby reduced the risk of alkaloid accumulation caused by tuber sprouting, which was favorable for potato storage and sales. From the perspective of seed potato breeding, nitrogen application markedly increased the number of sprouting eyes, resulting in more stems and higher tuber yield after replanting. Compared to the control, nitrogen application promoted the sprouting of eyes at the apical bud of potato tubers, improved associated α-amylase activity and sucrose content, and increased gibberellin 1 (GA 1) content by 6.0 times. Nitrogen application also facilitated stolon elongation and growth, increased associated GA 1 content by 2.2 times, and delayed the enlargement of the subapical region to form tubers by 6–15 d. Taken together, the results indicate that nitrogen management (increasing or reducing nitrogen application rate) can be used as an agricultural practice to regulate potato tuber dormancy and sprouting. The intrinsic link between regulation of tuber dormancy by nitrogen application rate and its effects on tuber development is attributable to the regulation of tuberization. This research provides abundant physiological information for tuber dormancy and development in potatoes. [ABSTRACT FROM AUTHOR]

• Selenium loss details was clarified during cooking of Se-enriched tubers. • Steaming resulted in the lowest selenium loss rate, followed by boiling and frying. • Selenium was almost completely lost after starch extraction. • Selenium application increased the diameter of starch granules. Selenium biofortification is increasingly applied to improve selenium contents in the edible parts of crops. Potato (Solanum tuberosum L.) is a major food crop with wide availability of consumption, which is suitable for selenium biofortification. However, the processing and product quality of selenium-enriched potatoes has rarely been reported. Herein, selenium-enriched potato tubers (0.24 mg kg−1 fresh weight) were used to investigate selenium retention, loss details, and quality changes in different processed products. Final selenium contents of the products varied with different processing methods (P <0.01). Compared to fresh tubers, steaming resulted in the lowest loss rate of selenium (28.64 %), mainly related to decoction. Moderate loss rates of selenium were recorded in boiled tubers (42.44 %), French fries (44.73 %), and crisps (50.86 %), mainly related to decoction, cutting and hot cleaning, respectively. The highest loss rate was attributed to starch extraction (98.69 %), mainly related to crude protein. Selenium application delayed enzymatic discoloration of fresh-cut tubers (P < 0.05) and increased the proportion of large- to medium-sized starch granules (>30 μm) (P < 0.05) compared to the control. To minimize selenium loss, steaming is superior to boiling and frying for the processing of selenium-enriched potatoes, and it is not feasible to produce selenium-enriched starch. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is an important nutrient for increased potato tuber yield. However, excessive N can decrease tuber quality. Furthermore, the impact of optimal and higher N levels of potato tuber metabolic profile at harvest and cold storage remains unclear. This study aimed to investigate the metabolic profiling of free amino acids and sugars in potato tubers affected by different nitrogen levels (optimal, ON; and excessive, EN) at harvest (AH) and cold storage (CS) (~4 °C, 4 weeks) through untargeted GC–TOF–MS, and targeted UHPLC–QqQ–MS. Carbohydrate content and vacuolar invertase activity (IV) were determined. Principal component analysis of metabolite data indicated a distinct separation between ON and EN treatments at harvest and cold storage. Multivariate data analysis revealed that sucrose, reducing sugars, and free asparagine were the most altered metabolites (VIP > 1 and P < 0.05), which were involved in starch and sucrose metabolism, and alanine, aspartate and glutamate metabolism. At harvest, the absolute contents of various free amino acids including asparagine were higher (by 1.3–1.5 fold) in the EN treatment than ON treatment, and this difference was maintained at 4-week cold storage. Under the EN treatment, tuber maturity was reduced, and sucrose accumulation was increased at harvest, while IV was increased after cold storage, reducing sugar also accumulated. These results highlighted the negative effects of EN on free amino acid and sugars metabolism in the post–harvest tubers and provided useful information for understanding the underpinning physiological mechanisms. Image 1 • The metabolic profiling of potato tubers was conducted under different N levels. • Multivariate analysis of metabolite data showed a distinct separation by N treatment. • Differential metabolites were involved in starch–sucrose and amino acid metabolism. • Free asparagine accumulation induced by excessive N was maintained after cold stress. • Excessive N treatment reduced tuber maturity and exacerbated cold-induced sweetening. [ABSTRACT FROM AUTHOR]

• Expression of StANS in chromatic potato tubers is significantly higher than that in yellow ones. • StANS gene can promote anthocyanin synthesis in potato tubers. • StANS can be regulated by transcription factors StAN2 , StMYB113 and StAN11. Anthocyanin synthase (ANS), a key enzyme in anthocyanins synthesis, can convert the colorless leucoanthocyanins into colored anthocyanins. In this study, a potato anthocyanin synthase gene StANS was isolated and characterized. Expression analysis showed that the transcriptional expression of StANS in chromatic genotypes was significantly higher than that in yellow ones. Overexpressing the StANS gene could promote anthocyanin synthesis in potato tubers. Transient luciferase assays showed that the promoter of StANS could be activated by the transcription factors StAN2 , StMYB113 , and StAN11. These results indicated that the StANS gene, which was activated by the transcription factors StAN2 , StMYB113 , and StAN11 , could promote the anthocyanins synthesis in potato tubers. These findings provide a theoretical and applicable basis for anthocyanins formation in colored potato tubers. [ABSTRACT FROM AUTHOR]

In this study, an isothermal reverse transcription-recombinase polymerase amplification (RT-RPA) assay was developed for the efficient and accurate detection of potato virus Y (PVY) under isothermal conditions. This RT-RPA assay was more efficient than the conventional reverse transcription-polymerase chain reaction (RT-PCR) assay as the amplification reaction can be completed in less than 20 min. Moreover, unlike PCR that requires a thermocycler to carry out the DNA amplification through specific temperature phases, RPA assay could be performed under an isothermal condition at a temperature ranging from 25 to 40 °C. A simple instrumentation such as a heating block or a water bath or even anon-instrumental condition such as human hands or a benchtop inside/outside a room during the summer could satisfy the temperature requirement of RPA. The sensitivity of this assay was equivalent to that of the conventional RT-PCR, and the virus can be detected in a minimum of 2 pg of total RNA extracted from the PVY infected potato leaf tissues. The efficacy of the newly developed RT-RPA was then evaluated using field potato leaf and dormancy-broken sprout samples upon enzyme-linked immunosorbent assay (ELISA) screening. Of the 164 PVY-ELISA-positive samples, RT-RPA detected 157 whereas simplex RT-PCR detected 160 and multiplex RT-PCR detected 154. Of the 74 randomly selected PVY-ELISA-negative samples, RT-RPA, simplex RT-PCR and multiplex RT-PCR led to 1, 1 and 0 positive detections, receptively. Overall, RT-RPA and the two RT-PCR assays as well as ELISA exhibited an agreement of 96.6–98.7%, thus demonstrating the suitability of RT-RPA for large scale detection of PVY, irrespective of the strain type of the virus. • An isothermal RT-RPA method has been developed for detection of PVY CP gene of all known strains. • This method could amplify the PVY target in less than 20 min with excellent flexibility in terms of temperature requirement ranging from 25 to 40 ℃. • This was the first report to evaluate the RT-RPA method for PVY detection at an under-equipped condition by using large scale of field samples. • Except for the RPA reaction, other steps of the assay procedure still needed to be optimized and simplified for fast on-site detection of PVY. [ABSTRACT FROM AUTHOR]