A Gram-negative pink-pigmented bacillus (named 2A) was isolated from Solanum tuberosum L. cv. Desirée plants that were strikingly more developed, presented increased root hair density, and higher biomass than other potato lines of the same age. The 16S ribosomal DNA sequence, used for comparative gene sequence analysis, indicated that strain 2A belongs to the genus Methylobacterium. Nucleotide identity between Methylobacterium sp. 2A sequenced genome and the rest of the species that belong to the genus suggested that this species has not been described so far. In vitro, potato plants inoculated with Methylobacterium sp. 2A had a better performance when grown under 50 mM NaCl or when infected with Phytophthora infestans. We inoculated Methylobacterium sp. 2A in Arabidopsis thaliana roots and exposed these plants to salt stress (75 mM NaCl). Methylobacterium sp. 2A-inoculated plants, grown in control or salt stress conditions, displayed a higher density of lateral roots (p < 0.05) compared to noninoculated plants. Moreover, under salt stress, they presented a higher number of leaves and larger rosette diameter. In dual confrontation assays, Methylobacterium sp. 2A displayed biocontrol activity against P. infestans, Botrytis cinerea, and Fusarium graminearum, but not against Rhizoctonia solani, and Pythium dissotocum. In addition, we observed that Methylobacterium sp. 2A diminished the size of necrotic lesions and reduced chlorosis when greenhouse potato plants were infected with P. infestans. Methylobacterium sp. 2A produces indole acetic acid, solubilizes mineral phosphate and is able to grow in a N 2 free medium. Whole-genome sequencing revealed metabolic pathways associated with its plant growth promoter capacity. Our results suggest that Methylobacterium sp. 2A is a plant growth-promoting rhizobacteria (PGPR) that can

We describe the potato CDPK family and place StCDPK7 as a player in potato response to Phytophthora infestans infection, identifying phenylalanine ammonia lyase as its specific phosphorylation target in vitro. Calcium-dependent protein kinases (CDPKs) decode calcium (Ca) signals and activate different signaling pathways involved in hormone signaling, plant growth, development, and both abiotic and biotic stress responses. In this study, we describe the potato CDPK/CRK multigene family; bioinformatic analysis allowed us to identify 20 new CDPK isoforms, three CDPK-related kinases (CRKs), and a CDPK-like kinase. Phylogenetic analysis indicated that 26 StCDPKs can be classified into four groups, whose members are predicted to undergo different acylation patterns and exhibited diverse expression levels in different tissues and in response to various stimuli. With the aim of characterizing those members that are particularly involved in plant-pathogen interaction, we focused on StCDPK7. Tissue expression profile revealed that StCDPK7 transcript levels are high in swollen stolons, roots, and mini tubers. Moreover, its expression is induced upon Phytophthora infestans infection in systemic leaves. Transient expression assays showed that StCDPK7 displays a cytosolic/nuclear localization in spite of having a predicted chloroplast transit peptide. The recombinant protein, StCDPK7:6xHis, is an active Ca-dependent protein kinase that can phosphorylate phenylalanine ammonia lyase, an enzyme involved in plant defense response. The analysis of the potato CDPK family provides the first step towards the identification of CDPK isoforms involved in biotic stress. StCDPK7 emerges as a relevant player that could be manipulated to deploy disease resistance in potato crops.

Among many factors that regulate potato tuberization, calcium and calcium-dependent protein kinases (CDPKs) play an important role. CDPK activity increases at the onset of tuber formation with StCDPK1 expression being strongly induced in swollen stolons. However, not much is known about the transcriptional and posttranscriptional regulation of StCDPK1 or its downstream targets in potato development. To elucidate further, we analyzed its expression in different tissues and stages of the life cycle. Histochemical analysis of StCDPK1::GUS (β-glucuronidase) plants demonstrated that StCDPK1 is strongly associated with the vascular system in stems, roots, during stolon to tuber transition, and in tuber sprouts. In agreement with the observed GUS profile, we found specific cis-acting elements in StCDPK1 promoter. In silico analysis predicted miR390 to be a putative posttranscriptional regulator of StCDPK1. Quantitative real time-polymerase chain reaction (qRT-PCR) analysis showed ubiquitous expression of StCDPK1 in different tissues which correlated well with Western blot data except in leaves. On the contrary, miR390 expression exhibited an inverse pattern in leaves and tuber eyes suggesting a possible regulation of StCDPK1 by miR390. This was further confirmed by Agrobacterium co-infiltration assays. In addition, in vitro assays showed that recombinant StCDPK1-6xHis was able to phosphorylate the hydrophilic loop of the auxin efflux carrier StPIN4. Altogether, these results indicate that StCDPK1 expression is varied in a tissue-specific manner having significant expression in vasculature and in tuber eyes; is regulated by miR390 at posttranscriptional level and suggest that StPIN4 could be one of its downstream targets revealing the overall role of this kinase in potato development.

When a plant detects a pathogen, chloroplasts terminate photosynthetic activity and uptake vital roles in the immune system to help stave off infection, including the production of defense hormone precursors and antimicrobial reactive oxygen species. Additionally, chloroplasts associate with the nucleus and produce greater numbers of tubular extensions called stromules during immune challenge. We previously showed that during infection by the potato blight pathogen Phytophthora infestans, chloroplasts accumulate at the pathogen haustoria, hyphal extensions that are accommodated within the host cell. However, the extent to which chloroplast positioning around haustoria, or at the nucleus, contributes to immunity during infection remains unknown. Here we show a striking increase in the susceptibility to P. infestans of Nicotiana benthamiana CRISPR knock-out lines lacking the chloroplast movement and anchoring gene, CHLOROPLAST UNUSUAL POSITIONING 1 (CHUP1). However, the positioning of chloroplasts around the haustorium or nucleus is not impaired in the absence of CHUP1. Further, loss of CHUP1 leads to an extreme clustering of chloroplasts around the nucleus in the presence and absence of infection, showing that greater chloroplast-nucleus association does not necessarily equate to more robust immunity. While plants lacking CHUP1 have reduced basal stromules, they are still able to induce stromules following immune stimulation, indicating that multiple populations of stromules exist. Lastly, we found that CHUP1 is required for proper deposition of callose - a cell wall material implicated in pathogen penetration resistance - around P. infestans haustorium, but not for other core immune processes. Our results implicate chloroplasts in plant focal immunity and point to a key role of CHUP1 in facilitating the deposition of defense material at the pathogen interface.

The benefits of the complex microscopic and industrially important group of microalgae such as diatoms is not hidden and have lately surprised the scientific community with their industrial potential. The ability to survive in harsh conditions and the presence of different pore structures and defined cell walls have made diatoms ideal cell machinery to produce a variety of industrial products. The prospect of using a diatom cell for industrial application has increased significantly in synch with the advances in microscopy, metabarcoding, analytical and genetic tools. Furthermore, it is well noted that the approach of industry and academia to the use of genetic tools has changed significantly, resulting in a well-defined characterization of various molecular components of diatoms. It is possible to conduct the primary culturing, harvesting, and further downstream processing of diatom culture in a cost-effective manner. Diatoms hold all the qualities to become the alternative raw material for pharmaceutical, nanotechnology, and energy sources leading to a sustainable economy. In this review, an attempt has been made to gather important progress in the different industrial applications of diatoms such as biotechnology, biomedical, nanotechnology, and environmental technologies.

Calcium-dependent protein kinases, CDPKs, decode calcium (Ca2+) transients and initiate downstream responses in plants. In order to understand how CDPKs affect plant physiology, their specific target proteins must be identified. In tobacco, the bZIP transcription factor Repression of Shoot Growth (NtRSG) that modulates gibberellin (GA) content is a specific target of NtCDPK1. StCDPK3 from potato is homologous (88% identical) to NtCDPK1 even in its N-terminal variable domain. In this work, we observe that NtRSG is also phosphorylated by StCDPK3. The potato RSG family of transcription factors is composed of three members that share similar features. The closest homologue to NtRSG, which was named StRSG1, was amplified and sequenced. qRT-PCR data indicate that StRSG1 is mainly expressed in petioles, stems, lateral buds, and roots. In addition, GA treatment affected StRSG1 expression. StCDPK3 transcripts were detected in leaves, petioles, stolons, roots, and dormant tubers, and transcript levels were modified in response to GA. The recombinant StRSG1-GST protein was produced and tested as a substrate for StCDPK3 and StCDPK1. 6xHisStCDPK3 was able to phosphorylate the potato StRSG1 in a Ca2+-dependent way, while 6xHisStCDPK1 could not. StCDPK3 also interacts and phosphorylates the transcription factor StABF1 (ABRE binding factor 1) involved in ABA signaling, as shown by EMSA and phosphorylation assays. StABF1 transcripts were mainly detected in roots, stems, and stolons. Our data suggest that StCDPK3 could be involved in the cross-talk between ABA and GA signaling at the onset of tuber development.

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Potato (Solanum tuberosum L.) tubers are an excellent staple food due to its high nutritional value. When the tuber reaches physiological competence, sprouting proceeds accompanied by changes at mRNA and protein levels. Potato tubers become a source of carbon and energy until sprouts are capable of independent growth. Transcript profiling of sprouts grown under continuous light or dark conditions was performed using the TIGR 10K EST Solanaceae microarray. The profiles analyzed show a core of highly expressed transcripts that are associated to the reactivation of growth. Under light conditions, the photosynthetic machinery was fully activated; the highest up-regulation was observed for the Rubisco activase (RCA), the glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the Photosystem II 22 kDa protein (CP22) genes, among others. On the other hand, sprouts exposed to continuous darkness elongate longer, and after extended darkness, synthesis of chloroplast components was repressed, the expression of proteases was reduced while genes encoding cysteine protease inhibitors (CPIs) and metallocarboxypeptidase inhibitors (MPIs) were strongly induced. Northern blot and RT-PCR analysis confirmed that MPI levels correlated with the length of the dark period; however, CPI expression was strong only after longer periods of darkness, suggesting a feedback loop (regulation mechanism) in response to dark-induced senescence. Prevention of cysteine protease activity in etiolated sprouts exposed to extended darkness could delay senescence until they emerge to light.