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.

Recent advances and challenges in potato improvement using CRISPR/Cas genome editing

Genome editing using CRISPR/Cas technology improves the quality of potato as a food crop and enables its use as both a model plant in fundamental research and as a potential biofactory for producing valuable compounds for industrial applications. Potato (Solanum tuberosum L.) plays a significant role in ensuring global food and nutritional security. Tuber yield is negatively affected by biotic and abiotic stresses, and enzymatic browning and cold-induced sweetening significantly contribute to post-harvest quality losses. With the dual challenges of a growing population and a changing climate, potato enhancement is essential for its sustainable production. However, due to several characteristics of potato, including high levels of heterozygosity, tetrasomic inheritance, inbreeding depression, and self-incompatibility of diploid potato, conventional breeding practices are insufficient to achieve substantial trait improvement in tetraploid potato cultivars within a relatively short time. CRISPR/Cas-mediated genome editing has opened new possibilities to develop novel potato varieties with high commercialization potential. In this review, we summarize recent developments in optimizing CRISPR/Cas-based methods for potato genome editing, focusing on approaches addressing the challenging biology of this species. We also discuss the feasibility of obtaining transgene-free genome-edited potato varieties and explore different strategies to improve potato stress resistance, nutritional value, starch composition, and storage and processing characteristics. Altogether, this review provides insight into recent advances, possible bottlenecks, and future research directions in potato genome editing using CRISPR/Cas technology.

Transcriptomic and proteomic data provide new insights into cold-treated potato tubers with T- and D-type cytoplasm

Tuber-omics in potato with the T- and D-types of cytoplasm showed different sets of differentially expressed genes and proteins in response to cold storage. For the first time, we report differences in gene and protein expression in potato (Solanum tuberosum L.) tubers possessing the T- or D-type cytoplasm. Two F1 diploid reciprocal populations, referred to as T and D, were used. The pooling strategy was applied for detection of differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) in tubers consisting of extreme chip colour after cold storage. RNA and protein bulks were constructed from contrasting phenotypes. We recognized 48 and 15 DEGs for the T and D progenies, respectively. DEPs were identified in the amyloplast and mitochondrial fractions. In the T-type cytoplasm, only 2 amyloplast-associated and 5 mitochondria-associated DEPs were detected. Of 37 mitochondria-associated DEPs in the D-type cytoplasm, there were 36 downregulated DEPs in the dark chip colour bulks. These findings suggest that T- and D-type of cytoplasm might influence sugar accumulation in cold-stored potato tubers in different ways. We showed that the mt/nucDNA ratio was higher in D-possessing tubers after cold storage than in T progeny. For the D-type cytoplasm, the pt/nucDNA ratio was higher for tubers characterized by dark chip colour than for those with light chip colour. Our findings suggest that T- and D-type cytoplasm might influence sugar accumulation in cold-stored potato tubers in different ways.

Transcriptional and proteomic insights into phytotoxic activity of interspecific potato hybrids with low glycoalkaloid contents

BACKGROUND

Glycoalkaloids are bioactive compounds that contribute to the defence response of plants against herbivore attack and during pathogenesis. Solanaceous plants, including cultivated and wild potato species, are sources of steroidal glycoalkaloids. Solanum plants differ in the content and composition of glycoalkaloids in organs. In wild and cultivated potato species, more than 50 steroidal glycoalkaloids were recognized. Steroidal glycoalkaloids are recognized as potential allelopathic/phytotoxic compounds that may modify the growth of target plants. There are limited data on the impact of the composition of glycoalkaloids on their phytotoxic potential.

RESULTS

The presence of α-solasonine and α-solamargine in potato leaf extracts corresponded to the high phytotoxic potential of the extracts. Among the differentially expressed genes between potato leaf bulks with high and low phytotoxic potential, the most upregulated transcripts in sample of high phytotoxic potential were anthocyanin 5-aromatic acyltransferase-like and subtilisin-like protease SBT1.7-transcript variant X2. The most downregulated genes were carbonic anhydrase chloroplastic-like and miraculin-like. An analysis of differentially expressed proteins revealed that the most abundant group of proteins were those related to stress and defence, including glucan endo-1,3-beta-glucosidase acidic isoform, whose expression level was 47.96× higher in potato leaf extract with low phytotoxic.

CONCLUSIONS

The phytotoxic potential of potato leaf extract possessing low glycoalkaloid content is determined by the specific composition of these compounds in leaf extract, where α-solasonine and α-solamargine may play significant roles. Differentially expressed gene and protein profiles did not correspond to the glycoalkaloid biosynthesis pathway in the expression of phytotoxic potential. We cannot exclude the possibility that the phytotoxic potential is influenced by other compounds that act antagonistically or may diminish the glycoalkaloids effect.

Comparative proteomic analysis of resistant and susceptible potato cultivars during Synchytrium endobioticum infestation

We report the first comparative study of protein expression profiles in tuber sprouts between Katahdin-derived potato cultivars resistant and susceptible to Synchytrium endobioticum. Synchytrium endobioticum causes wart disease in potato (Solanum tuberosum L.) and is considered as the most important quarantine pathogen in almost all countries where potatoes are grown. We performed a comparative analysis of differentially expressed proteins in the tuber sprouts of potato cultivars differing in resistance to pathotype 1(D1) of S. endobioticum using two-dimensional electrophoresis (2-DE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) approaches. Bulks prepared from two resistant (Calrose and Humalda) and three susceptible (Sebago, Seneca and Wauseon) potato cultivars were studied. When protein profiles were compared between mock- and S. endobioticum-inoculated sprouts, 35 and 63 protein spots, indicating qualitative or quantitative differences, were detected in the resistant and susceptible cultivars, respectively. In turn, 24 proteins associated with resistance to S. endobioticum were revealed by comparison of the resistant and susceptible bulks. These proteins were changed in a constitutive or induced manner and were grouped into four categories: stress and defence, cell structure, protein turnover, and metabolism. Among the 13 proteins classified into the stress and defence group, seven proteins were related to heat-shock proteins (HSPs)/chaperone factors. In addition, four proteins, S-adenosyl-L-homocysteine hydrolase-like, superoxide dismutase [Mn], inactive patatin-3-Kuras 1 and patatin-15, were induced in the resistant bulk; whereas two proteins, patatin-01 and nucleoredoxin 1, showed significant differences in expression between the S. endobioticum-inoculated resistant and susceptible bulks. The detection of such a large number of S. endobioticum-mediated proteins representing the HSP70, HSP60 and HSP20 families suggests their significant role in restricting wart disease in potato tubers.

Mapping of quantitative trait loci for tuber starch and leaf sucrose contents in diploid potato

Most QTL for leaf sucrose content map to positions that are similar to positions of QTL for tuber starch content in diploid potato. In the present study, using a diploid potato mapping population and Diversity Array Technology (DArT) markers, we identified twelve quantitative trait loci (QTL) for tuber starch content on seven potato chromosomes: I, II, III, VIII, X, XI, and XII. The most important QTL spanned a wide region of chromosome I (42.0–104.6 cM) with peaks at 63 and 84 cM which explained 17.6 and 19.2% of the phenotypic variation, respectively. ADP-glucose pyrophosphorylase (AGPase) is the key enzyme for starch biosynthesis. The gene encoding the large subunit of this enzyme, AGPaseS-a, was localized to chromosome I at 102.3 cM and accounted for 15.2% of the variance in tuber starch content. A more than 100-fold higher expression of this gene was observed in RT-qPCR assay in plants with the marker allele AGPaseS-a1334. This study is the first to report QTL for sucrose content in potato leaves. QTL for sucrose content in leaves were located on eight potato chromosomes: I, II, III, V, VIII, IX, X and XII. In 5-week-old plants, only one QTL for leaf sucrose content was detected after 8 h of darkness; four QTL were detected after 8 h of illumination. In 11-week-old plants, 6 and 3 QTL were identified after dark and light phases, respectively. Of fourteen QTL for leaf sucrose content, eleven mapped to positions that were similar to QTL for tuber starch content. These results provide genetic information for further research examining the relationships between metabolic carbon molecule sources and sinks in potato plants.

Novel candidate genes AuxRP and Hsp90 influence the chip color of potato tubers

Potato (Solanum tuberosum L.) tubers exhibit significant variation in reducing sugar content directly after harvest, cold storage and reconditioning. Here, we performed QTL analysis for chip color, which is strongly influenced by reducing sugar content, in a diploid potato mapping population. Two QTL on chromosomes I and VI were detected for chip color after harvest and reconditioning. Only one region on chromosome VI was linked with cold-induced sweetening. Using the RT-PCR technique, we showed differential expression of the auxin-regulated protein (AuxRP) gene. The AuxRP transcript was presented in light chip color parental clone DG 97-952 and the RNA progeny of the bulk sample consisting of light chip color phenotypes after cold storage. This amplicon was absent in dark chip parental clone DG 08-26/39 and the RNA bulk sample of dark chip progeny. Genetic variation of AuxRP explained up to 16.6 and 15.2 % of the phenotypic variance after harvest and 3 months of storage at 4 °C, respectively. Using an alternative approach, the RDA-cDNA method was used to recognize 25 gene sequences, of which 11 could be assigned to potato chromosome VI. One of these genes, Heat-shock protein 90 (Hsp90), demonstrated higher mRNA and protein expression in RT-qPCR and western blotting assays in the dark chip color progeny bulk sample compared with the light chip color progeny bulk sample. Our study, for the first time, suggests that the AuxRP and Hsp90 genes are novel candidate genes capable of influencing the chip color of potato tubers.