Mutation in the Arabidopsis regulatory-associated protein TOR 1B (RAPTOR1B) leads to decreased jasmonates levels in leaf tissue

Glycolysis and signal transduction participate in Lycium barbarum in response to NaCl stress through protein phosphorylation

BACKGROUND

Lycium barbarum L. possesses great salt tolerance and medicinal values, studying its salt tolerance contribute to variety improvement, as well as the increase in yield and quality.

RESULTS

The study integrated the tandem mass tags (TMT) phosphoproteomics and physiological indexes of L. barbarum exposed to different concentrations of NaCl, with the aim of characterizing salt adaptation characteristics of L. barbarum. The findings indicated that a total of 2189 differentially phosphorylated peptides were identified, functional analysis revealed their involvement in glycolysis, plant hormone signal transduction, mitogen-activated protein kinase (MAPK) signal transduction and other pathways, and that the enzyme activities and substances related to glycolysis and signal transduction underwent significant changes under salt stress.

CONCLUSION

Salt stress enhanced the glycolysis pathway through protein phosphorylation, and the changes in related enzymes activity accelerated the conversion of intermediate metabolites and energy supply. Salt stress led to the accumulation of abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) levels, triggering signal transduction events regulated by phosphorylated proteins to improve salt tolerance for L. barbarum in saline environments. The phosphorylation of MAPK signaling pathway-related proteins is triggered by reactive oxygen species (ROS) and ABA as signal molecules to induce the expression of downstream salt stress response factors. This study provides a foundation for further analysis of the molecular regulatory mechanism of protein phosphorylation in L. barbarum for salt stress.

Transcriptomic analysis of regulating the growth and development of tomato seedlings by the crosstalk between JA and TOR signaling

KEY MESSAGE

Transcription factors MYB, WRKY, bHLH, bZIP and NAC were identified as key candidate genes for JA and TOR regulation of tomato seedling growth and development. Jasmonic acid (JA) and Target of Rapamycin (TOR) signaling pathways interact to regulate plant growth, development, and stress responses. In this study, transcriptomic and weighted gene co-expression network analysis (WGCNA) were conducted on tomato wild-type (WT) and spr2 mutant lines treated with the TOR inhibitor RAP and activator MHY1485. We identified key roles of MAPK kinase and ethylene signaling in mediating JA-TOR interaction. Core transcription factors, including MYB, WRKY, bHLH, bZIP, and NAC, were highlighted as central regulators within the interaction between JA and TOR signaling network. These findings advance our understanding of how JA and TOR signaling coordinate plant growth and stress adaptation.

SlMYC2 interacted with the SlTOR promoter and mediated JA signaling to regulate growth and fruit quality in tomato

Tomato (Solanum lycopersicum) is a major vegetable crop cultivated worldwide. The regulation of tomato growth and fruit quality has long been a popular research topic. MYC2 is a key regulator of the interaction between jasmonic acid (JA) signaling and other signaling pathways, and MYC2 can integrate the interaction between JA signaling and other hormone signals to regulate plant growth and development. TOR signaling is also an essential regulator of plant growth and development. However, it is unclear whether MYC2 can integrate JA signaling and TOR signaling during growth and development in tomato. Here, MeJA treatment and SlMYC2 overexpression inhibited the growth and development of tomato seedlings and photosynthesis, but increased the sugar-acid ratio and the contents of lycopene, carotenoid, soluble sugar, total phenol and flavonoids, indicating that JA signaling inhibited the growth of tomato seedlings and altered fruit quality. When TOR signaling was inhibited by RAP, the JA content increased, and the growth and photosynthesis of tomato seedlings decreased, indicating that TOR signaling positively regulated the growth and development of tomato seedlings. Further yeast one-hybrid assays showed that SlMYC2 could bind directly to the SlTOR promoter. Based on GUS staining analysis, SlMYC2 regulated the transcription of SlTOR, indicating that SlMYC2 mediated the interaction between JA and TOR signaling by acting on the promoter of SlTOR. This study provides a new strategy and some theoretical basis for tomato breeding.

To grow or not to grow under nutrient scarcity: Target of rapamycin-ethylene is the question

To cope with nutrient scarcity, plants generally follow two main complementary strategies. On the one hand, they can slow down growing, mainly shoot growth, to diminish the demand of nutrients. We can call this strategy as "stop growing." On the other hand, plants can develop different physiological and morphological responses, mainly in their roots, aimed to facilitate the acquisition of nutrients. We can call this second strategy as "searching for nutrients." Both strategies are compatible and can function simultaneously but the interconnection between them is not yet well-known. In relation to the "stop growing" strategy, it is known that the TOR (Target Of Rapamycin) system is a central regulator of growth in response to nutrients in eukaryotic cells. TOR is a protein complex with kinase activity that promotes protein synthesis and growth while some SnRK (Sucrose non-fermenting 1-Related protein Kinases) and GCN (General Control Non-derepressible) kinases act antagonistically. It is also known that some SnRKs and GCNs are activated by nutrient deficiencies while TOR is active under nutrient sufficiency. In relation to the "searching for nutrients" strategy, it is known that the plant hormone ethylene participates in the activation of many nutrient deficiency responses. In this Mini Review, we discuss the possible role of ethylene as the hub connecting the "stop growing" strategy and the "searching for nutrients" strategy since very recent results also suggest a clear relationship of ethylene with the TOR system.

Target of rapamycin (TOR) regulates the response to low nitrogen stress via autophagy and hormone pathways in Malus hupehensis

Target of rapamycin (TOR) is a highly conserved master regulator in eukaryotes; it regulates cell proliferation and growth by integrating different signals. However, little is known about the function of TOR in perennial woody plants. Different concentrations of AZD8055 (an inhibitor of TOR) were used in this study to investigate the role of TOR in the response to low nitrogen (N) stress in the wild apple species Malus hupehensis. Low N stress inhibited the growth of M. hupehensis plants, and 1 μM AZD alleviated this effect. Plants supplied with 1 μM AZD had higher photosynthetic capacity, which promoted the accumulation of biomass, as well as higher contents of N and anthocyanins and lower content of starch. Exogenous application of 1 μM AZD also promoted the development of the root system. Plants supplied with at least 5 μM AZD displayed early leaf senescence. RNA-seq analysis indicated that TOR altered the expression of genes related to the low N stress response, such as genes involved in photosystem, starch metabolism, autophagy, and hormone metabolism. Further analysis revealed altered autophagy in plants supplied with AZD under low N stress; the metabolism of plant hormones also changed following AZD supplementation. In sum, our findings revealed that appropriate inhibition of TOR activated autophagy and jasmonic acid signaling in M. hupehensis, which allowed plants to cope with low N stress. Severe TOR inhibition resulted in the excessive accumulation of salicylic acid, which probably led to programmed cell death in M. hupehensis.

A Tour of TOR Complex Signaling in Plants

To identify the appropriate times for growth and development, organisms must sense and process information about the availability of nutrients, energy status, and environmental cues. For sessile eukaryotes such as plants, integrating such information can be critical in life or death decisions. For nearly 30 years, the conserved phosphatidylinositol 3-kinase-related protein kinases (PIKKs) target of rapamycin (TOR) has been established as a central hub for integrating external and internal metabolic cues. Despite the functional conservation across eukaryotes, the TOR complex has evolved specific functional and mechanistic features in plants. Here, we present recent findings on the plant TOR complex that highlight the conserved and unique nature of this critical growth regulator and its role in multiple aspects of plant life.