Molecular Insights into the Accelerated Sprouting of and Apical Dominance Release in Potato Tubers Subjected to Post-Harvest Heat Stress.

Climate change-induced heat stress (HS) increasingly threatens potato (Solanum tuberosum L.) production by impacting tuberization and causing the premature sprouting of tubers grown during the hot season. However, the effects of post-harvest HS on tuber sprouting have yet to be explored. This study aims to investigate the effects of post-harvest HS on tuber sprouting and to explore the underlying transcriptomic changes in apical bud meristems. The results show that post-harvest HS facilitates potato tuber sprouting and negates apical dominance. A meticulous transcriptomic profiling of apical bud meristems unearthed a spectrum of differentially expressed genes (DEGs) activated in response to HS. During the heightened sprouting activity that occurred at 15-18 days of HS, the pathways associated with starch metabolism, photomorphogenesis, and circadian rhythm were predominantly suppressed, while those governing chromosome organization, steroid biosynthesis, and transcription factors were markedly enhanced. The critical DEGs encompassed the enzymes pivotal for starch metabolism, the genes central to gibberellin and brassinosteroid biosynthesis, and influential developmental transcription factors, such as SHORT VEGETATIVE PHASE, ASYMMETRIC LEAVES 1, SHOOT MERISTEMLESS, and MONOPTEROS. These findings suggest that HS orchestrates tuber sprouting through nuanced alterations in gene expression within the meristematic tissues, specifically influencing chromatin organization, hormonal biosynthesis pathways, and the transcription factors presiding over meristem fate determination. The present study provides novel insights into the intricate molecular mechanisms whereby post-harvest HS influences tuber sprouting. The findings have important implications for developing strategies to mitigate HS-induced tuber sprouting in the context of climate change.

Proteomic Analysis of Potato Responding to the Invasion of Ralstonia solanacearum UW551 and Its Type III Secretion System Mutant.

The infection of potato with Ralstonia solanacearum UW551 gives rise to bacterial wilt disease via colonization of roots. The type III secretion system (T3SS) is a determinant factor for the pathogenicity of R. solanacearum. To fully understand perturbations in potato by R. solanacearum type III effectors(T3Es), we used proteomics to measure differences in potato root protein abundance after inoculation with R. solanacearum UW551 and the T3SS mutant (UW551△HrcV). We identified 21 differentially accumulated proteins. Compared with inoculation with UW551△HrcV, 10 proteins showed significantly lower abundance in potato roots after inoculation with UW551, indicating that those proteins were significantly downregulated by T3Es during the invasion. To identify their functions in immunity, we silenced those genes in Nicotiana benthamiana and tested the resistance of the silenced plants to the pathogen. Results showed that miraculin, HBP2, and TOM20 contribute to immunity to R. solanacearum. In contrast, PP1 contributes to susceptibility. Notably, none of four downregulated proteins (HBP2, PP1, HSP22, and TOM20) were downregulated at the transcriptional level, suggesting that they were significantly downregulated at the posttranscriptional level. We further coexpressed those four proteins with 33 core T3Es. To our surprise, multiple effectors were able to significantly decrease the studied protein abundances. In conclusion, our data showed that T3Es of R. solanacearum could subvert potato root immune-related proteins in a redundant manner.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Modulation of gene expression in cold-induced sweetening resistant potato species Solanum berthaultii exposed to low temperature.

Cold-induced sweetening (CIS) is a crucial factor influencing the processing quality of potato tubers. To better understand the molecular events of potato CIS and different CIS-sensitivity among various potato species, a suppression subtractive hybridization library and cDNA microarray gene filters were developed. A total of 188 genes were found to be differentially expressed (DE) in Solanum berthaultii (ber) upon cold stimulation. These functional genes were mostly related to cell rescue, defense and virulence, metabolism, energy and protein fate, included in various processes of plant defense against abiotic stresses. Four expression patterns of these DE genes were profiled by qRT-PCR using the cold-stored tubers of both CIS-resistant (ber) and CIS-sensitive (E-potato 3, a variety of S. tuberosum) potatoes. The expression pattern and abundance of many DE genes encoding proteins involved in metabolism were different in these two potato tubers, especially genes associated with amylolysis, sucrose decomposition and glycolysis pathways, indicating distinct regulatory mechanisms between ber and E3 in response to cold stress, which may be crucial for potato CIS. Further investigation of these cold-regulated genes will deepen our understanding of the regulatory mechanisms of potato CIS and direct approaches for the genetic improvement of potato processing quality.

A new isoform of thioredoxin h group in potato, SbTRXh1, regulates cold-induced sweetening of potato tubers by adjusting sucrose content.

UNLABELLED: In order to study the molecular mechanism of the cold-induced sweetening (CIS) of potato tubers, a novel isoform of thioredoxin h group, SbTRXh1, which was up-regulated early in the 4 °C storage of CIS-resistant potato (Solanum berthaultii) tubers, was cloned in present research. The genetic transformation of over-expression (OE) and RNA interference (RNAi) of SbTRXh1 into potato cv. E-Potato 3 (E3) was carried out to clarify its function in CIS regulation. The results showed that the transcripts of SbTRXh1 in either OE- or RNAi-tubers were strongly induced in 4 °C storage and quantitatively related to the reducing sugar (RS) accumulation, indicating that SbTRXh1 is involved in the CIS process of potato tubers. Regression analysis between the transcripts and protein contents of SbTRXh1 showed a very significant logarithmic relationship implying that the expression of SbTRXh1 may be mainly regulated at transcriptional level. Further monitoring the variation of the sugar contents in cold-stored tubers demonstrated a linear relationship between RS and sucrose (Suc). Thus, it can be inferred that SbTRXh1 may function in the Suc-RS pathway for CIS regulation of potato tubers. KEY MESSAGE: SbTRXh1 is primarily demonstrated to be involved in the regulation of cold-induced sweetening (CIS) of potato tubers, and it may function in the Suc-RS pathway for CIS regulation.