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Cold-induced sweetening (CIS), the undesirable sugar accumulation in cold-stored potato (Solanum tuberosumL.) tubers, is a severe postharvest issue in the potato processing industry. Although the process of sucrose hydrolysis by vacuolar invertase during potato CIS is well understood, there is limited knowledge about the transportation of sucrose from the cytosol to the vacuole during postharvest cold storage. Here, we report that among the three potato tonoplast sugar transporters (TSTs), StTST1exhibits the highest expression in tubers during postharvest cold storage. Subcellular localization analysis demonstrates that StTST1 is a tonoplast-localized protein. StTST1knockdown decreases reducing sugar accumulation in tubers during low-temperature storage. Compared to wild-type, potato chips produced from StTST1-silenced tubers displayed significantly lower acrylamide levels and lighter color after cold storage. Transcriptome analysis manifests that suppression of StTST1promotes starch synthesis and inhibits starch degradation in cold-stored tubers. We further establish that the increased sucrose content in the StTST1-silenced tubers might cause a decrease in the ABA content, thereby inhibiting the ABA-signaling pathway. We demonstrate that the down-regulation of β-amylase StBAM1in StTST1-silenced tubers might be directly controlled by ABA-responsive element-binding proteins (AREBs). Altogether, we have shown that StTST1plays a critical role in sugar accumulation and starch metabolism regulation during postharvest cold storage. Thus, our findings provide a new strategy to improve the frying quality of cold-stored tubers and reduce the acrylamide content in potato chips.

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 PVYO, PVYN:O, PVYNTNand PVYN. 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 PVYN:O/PVYNTN/PVYNafter either mechanical or graft inoculation, indicating susceptibility of the cultivar to these PVY strains. The cultivar was also infected readily with PVYOafter graft inoculation. However, despite induction of local lesions on the inoculated leaves, mechanical inoculation with PVYOmay 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 PVYO. Analysis of a segregating population of F87084 × F02010 revealed that the ER in F87084 is controlled by a dominant resistance gene. La variedad de papa Exploits y el clon avanzado F87084 han sido considerados como resistentes al virus Y de la papa (PVY). Para una mayor exploración sobre el grado de resistencia y determinar si la resistencia es específica por variante viral, estos materiales, junto con la variedad Rochdale Gold-Dorée y la línea avanzada F02010, se investigaron para su respuesta a diferentes variantes del PVY, incluyendo PVYO, PVYN:O, PVYNTN y PVYN. Tanto F02010 como Rochdale Gold-Dorée fueron fácilmente infectadas con todas las variantes de prueba después de inoculación mecánica o por injerto, indicando susceptibilidad de los materiales al PVY. No fue posible infectar al clon F87084 por cualquiera de las variantes probadas de PVY y tampoco se encontró nivel detectable de PVY mediante ELISA en las plantas después de inoculación mecánica o por injerto, demostrando resistencia extrema en F87084 a todas las variantes probadas de PVY. Se infectó a Exploits con PVYN:O/PVYNTN/PVYN después de inoculación mecánica o injerto, indicando susceptibilidad de la variedad a estas variantes del PVY. La variedad también fue fácilmente infectada con PVYO después de la inoculación por injerto. No obstante, a pesar de la inducción de lesiones locales en las hojas inoculadas, la inoculación mecánica con PVY puede o no conducir a síntomas sistémicos y a nivel de PVY detectable por ELISA, dependiendo de la temperatura. A baja temperatura (ej. 22ºC) no se encontraron síntomas sistémicos visibles o niveles de PVY detectables por ELISA en las plantas; mientras que a alta temperatura (ej. 30ºC), se detectaron síntomas sistémicos y alto nivel de PVY. Estos resultados demuestran que Exploits tiene resistencia hipersensible al PVYO dependiente de la temperatura. Un análisis de la población segregante de F87084 x F02010 reveló que la ER en F87084 es controlada por un gene dominante de resistencia.

The potato plantlets singly infected by PVA, PLRV, PVS, PVX and PVY and mix-infected by PVM, PVS and PVY were cultured on MS medium with different concentration of ribavirin. The effects of ribavirin on growth of the plantlets and efficiency of virus elimination were investigated. Results showed that the plant height and fresh weight obviously decreased with increase of ribavirin concentration from 0 mg/L to 150 mg/L, and most of the plantlets could not survive when the concentration reached 200 mg/L. According to the ELISA tests, ribavirin was more efficient for eradicating PVA, PVM, PVS and PVX than PVY and PLRV, and healthy plantlets could be obtained with high frequency (up to 100 %) by culturing with 75 ~ 150 mg/L ribavirin after 2 ~ 3 subcultures. Whereas, only 33 ~ 66 % PVY and PLRV infected plantlets were found to be virus-free after 3 subcultures with 75 ~ 150 mg/L ribavirin. The results of quantitative RT-PCR (qPCR) indicated that ribavirin could obviously reduce virus content in the plantlets. Except PLRV was detected positive after 3 subcultures with ribavirin, the healthy seedlings were obtained from infected stocks at the first or end of propagation and no viruses could be detected at the post-eradication stage. No apparent difference of genetic variation resulted from ribavirin treatment was found by SSR analysis between the control and the treated plantlets. All of these results above proved that ribavirin treatment in vitro was an effective method to eliminate viruses in the propagation of potato. Las plántulas de papa infectadas individualmente con los virus PVA, PLRV, PVS, PVX y PVY e infectadas con la mezcla de PVM, PVS y PVY, se cultivaron en un medio MS con diferentes concentraciones de ribavirin. Se investigaron los efectos de ribavirin en el crecimiento de las plántulas y la eficiencia en la eliminación de virus. Los resultados demostraron que la altura de la planta y el peso fresco disminuyeron obviamente con el aumento en la concentración de ribavirin de 0 mg/L a 150 mg/L, y la mayoría de las plántulas no sobrevivieron cuando la concentración alcanzó 200 mg/L. De acuerdo con las pruebas de ELISA, ribavirin fue más eficiente en la erradicación de PVA, PVM, PVS y PVX, que en la de PVY y PLRV, y se pudieron obtener plántulas sanas con alta frecuencia (hasta de 100 %) mediante el cultivo con 75 ~ 150 mg/L de ribavirin después de 2 ~ 3 subcultivos, mientras que solo 33 ~ 66 % de plántulas infectadas con PVY y PLRV se encontraron libres de virus después de tres subcultivos con 75 ~ 150 mg/L de ribavirin. Los resultados de RT-PCR (qPCR) cuantitativos indicaron que ribavirin pudo reducir obviamente el contenido de virus en las plántulas. Excepto por el PLRV que fue detectado después de tres subcultivos con ribavirin, las plántulas sanas se obtuvieron de lotes infectados al principio o al final de la propagación y no se pudieron detectar virus en la etapa de post-erradicación. No hubo diferencia aparente en variación genética del tratamiento con ribavirin mediante análisis SSR entre las plántulas testigo y las tratadas. Estos resultados prueban que el tratamiento in vitro con ribavirin fue un método efectivo para eliminar virus en la propagación in vitro de papa.

Plant viruses recruit multiple host factors for translation, replication, and movement in the infection process. The loss-of-function mutation of the susceptibility genes will lead to the loss of susceptibility to viruses, which is referred to as ‘recessive resistance’. Essential for potexvirus Accumulation 1(EXA1)has been identified as a susceptibility gene required for potexvirus, lolavirus, and bacterial and oomycete pathogens. In this study, EXA1knockdown in potato (StEXA1) was found to confer novel resistance to potato virus Y (PVY, potyvirus) in a strain-specific manner. It significantly compromised PVYOaccumulation but not PVYN:Oand PVYNTN. Further analysis revealed that StEXA1 is associated with the HC-Pro of PVY through a member of eIF4Es (StnCBP). HC-ProOand HC-ProN, two HC-Pro proteins from PVYOand PVYN, exhibited strong and weak interactions with StnCBP, respectively, due to their different spatial conformation. Moreover, the accumulation of PVYOwas mainly dependent on the stress granules (SGs) induced by StEXA1 and StnCBP, whereas PVYN:Oand PVYNTNcould induce SGs by HC-ProNindependently through an unknown mechanism. These results could explain why StEXA1or StnCBPknockdown conferred resistance to PVYObut not to PVYN:Oand PVYNTN. In summary, our results for the first time demonstrate that EXA1can act as a susceptibility gene for PVY infection. Finally, a hypothetical model was proposed for understanding the mechanism by which StEXA1 interacts with StnCBP to facilitate PVY accumulation in potato through the SG-dependent RNA regulatory pathway.