Pre-Anthesis Cytokinin Applications Increase Table Grape Berry Firmness by Modulating Cell Wall Polysaccharides

Unveiling key mechanisms: Transcriptomic meta-analysis of diverse nanomaterial applications addressing biotic and abiotic stresses in Arabidopsis Thaliana

The potential applications of nanomaterials in agriculture for alleviating diverse biotic and abiotic stresses have garnered significant attention. The reported mechanisms encompass promoting plant growth and development, alleviating oxidative stress, inducing defense responses, modulating plant-microbe interactions, and more. However, individual studies may not fully uncover the common pathways or distinguish the effects of different nanostructures. We examined Arabidopsis thaliana transcriptomes exposed to biotic, abiotic, and metal or carbon-based nanomaterials, utilizing 24 microarray chipsets and 17 RNA-seq sets. The results showed that: 1) from the perspective of different nanostructures, all metal nanomaterials relieved biotic/abiotic stresses via boosting metal homeostasis, particularly zinc and iron. Carbon nanomaterials induce hormone-related immune responses in the presence of both biotic and abiotic stressors. 2) Considering the distinct features of various nanostructures, metal nanomaterials displayed unique characteristics in seed priming for combating abiotic stresses. In contrast, carbon nanomaterials exhibited attractive features in alleviating water deprivation and acting as signaling amplifiers during biotic stress. 3) For shared pathway analysis, response to hypoxia emerges as the predominant and widely shared regulatory mechanism governing diverse stress responses, including those induced by nanomaterials. By deciphering shared and specific pathways and responses, this research opens new avenues for precision nano-agriculture, offering innovative strategies to optimize plant resilience, improve stress management, and advance sustainable crop production practices.

Insights into the cell-wall dynamics in grapevine berries during ripening and in response to biotic and abiotic stresses

The cell wall (CW) is the dynamic structure of a plant cell, acting as a barrier against biotic and abiotic stresses. In grape berries, the modifications of pulp and skin CW during softening ensure flexibility during cell expansion and determine the final berry texture. In addition, the CW of grape berry skin is of fundamental importance for winemaking, controlling secondary metabolite extractability. Grapevine varieties with contrasting CW characteristics generally respond differently to biotic and abiotic stresses. In the context of climate change, it is important to investigate the CW dynamics occurring upon different stresses, to define new adaptation strategies. This review summarizes the molecular mechanisms underlying CW modifications during grapevine berry fruit ripening, plant-pathogen interaction, or in response to environmental stresses, also considering the most recently published transcriptomic data. Furthermore, perspectives of new biotechnological approaches aiming at modifying the CW properties based on other crops' examples are also presented.

Proteomic and Low-Polar Metabolite Profiling Reveal Unique Dynamics in Fatty Acid Metabolism during Flower and Berry Development of Table Grapes

Grapevine development and ripening are complex processes that involve several biochemical pathways, including fatty acid and lipid metabolism. Fatty acids are essential components of lipids, which play crucial roles in fruit maturation and flavor development. However, the dynamics of fatty acid metabolism in grape flowers and berries are poorly understood. In this study, we present those dynamics and investigate the mechanisms of fatty acid homeostasis on 'Thompson Seedless' berries using metabolomic and proteomic analyses. Low-polar metabolite profiling indicated a higher abundance of fatty acids at the pre-flowering and pre-veraison stages. Proteomic analyses revealed that grape flowers and berries display unique profiles of proteins involved in fatty acid biosynthesis, triacylglycerol assembly, fatty acid β-oxidation, and lipid signaling. These findings show, for the first time, that fatty acid metabolism also plays an important role in the development of non-oil-rich tissues, opening new perspectives about lipid function and its relation to berry quality.

Proteomic and metabolomic integration reveals the effects of pre-flowering cytokinin applications on central carbon metabolism in table grape berries

Consumers around the world prefer high quality table grapes. To achieve higher quality traits at ripening, grapevine producers apply different plant growth regulators. The synthetic cytokinin forchlorfenuron N-(2-chloro-4-pyridinyl)-N'-phenylurea (CPPU) is widely used, its effect on grape quality is poorly understood. We hypothesized that the use of CPPU in pre-flowering can lead to changes in the metabolism that affects grape quality at harvest. Therefore, we investigated the role of CPPU applications on the quality of grapes by integrating proteomics and metabolomics. CPPU-treated grapevines showed a significant increase in berry size and firmness. Proteomic analyses indicated that CPPU-treated berries accumulated enzymes associated with carbohydrate metabolism, glycolysis, and tricarboxylic acid (TCA) cycle at harvest. Metabolomic analyses showed shifts in the abundance of compounds associated with carbohydrate metabolism and TCA cycle in CPPU-treated grapes. These findings suggest that CPPU applications modulate central carbon metabolism, improving grape berry quality.

Melatonin triggers tissue-specific changes in anthocyanin and hormonal contents during postharvest decay of Angeleno plums

Plum is a stone fruit that stands out for having a short shelf-life because of its high susceptibility to rapid deterioration. Part of this deterioration is explained by fruit overripening. Recently, the role of melatonin in delaying postharvest decay has been investigated but its regulatory function during overripening is still under extensive debate. In this study, to understand physiological events taking place in plums overripening and elucidate the role of melatonin on the postharvest quality of these fruits and its relationship to other plant hormones, Angeleno plums were sprayed with 10^-4 M of melatonin solution immediately after harvest. We carried out tissue-specific (mesocarp and exocarp) analysis of total phenols and anthocyanin quantification, as well as the evaluation of different phytohormones by LC-MS/MS and fruit quality parameters. Results showed that during postharvest, endogenous melatonin contents decreased both in the mesocarp and the exocarp of Angeleno plums. Likewise, plum firmness also decreased and a strong correlation was found for this parameter with jasmonic acid (JA) and cytokinins. Conversely, after exogenous melatonin application, endogenous melatonin content increased both in mesocarp and exocarp but it had a differential effect depending on the plum tissue. Indeed, total phenol and anthocyanin contents arose by 21% and 58%, respectively, in the mesocarp after melatonin treatment but no variations were found in the exocarp of Angeleno plums. Hormonal analysis of Angeleno mesocarp also revealed an increase in the JA and its precursor, 12-oxo-phytodienoic acid (OPDA), on the fourth day after melatonin application as well as a positive correlation between melatonin and gibberellin 1 (GA₁). These results suggest that melatonin may be acting as a signal molecule increasing phenolic compounds contents through direct regulation and by signaling with other phytohormones. Therefore, this research provides valuable information for understanding the regulatory role of melatonin and its relationship with plant hormones during overripening to contribute to improve the postharvest quality of plums.

Metabolomic and biochemical analysis of mesocarp tissues from table grape berries with contrasting firmness reveals cell wall modifications associated to harvest and cold storage

Tissue texture influences the grape berry consumers acceptance. We studied the biological differences between the inner and outer mesocarp tissues in hard and soft berries of table grapes cv NN107. Texture analysis revealed lower levels of firmness in the inner mesocarp as compared with the outer tissue. HPAEC-PAD analysis showed an increased abundance of cell wall monosaccharides in the inner mesocarp of harder berries at harvest. Immunohistochemical analysis displayed differences in homogalacturonan methylesterification and cell wall calcium between soft and hard berries. This last finding correlated with a differential abundance of calcium measured in the alcohol-insoluble residues (AIR) of the inner tissue of the hard berries. Analysis of abundance of polar metabolites suggested changes in cell wall carbon supply precursors, providing new clues in the identification of the biochemical factors that define the texture of the mesocarp of grape berries.