Physiological Responses to Abiotic Stresses
. In The Olive Tree Genome
; The Olive Tree Genome; Springer International Publishing: Cham, 2016; pp. 99 - 122. Publisher's VersionAbstract
Olive (Olea europaea L.) trees are widespread in Mediterranean agroecosystems and are now extensively cultivated in different warm-temperate regions of the world such as North and South America, Australia, New Zealand, and South Africa, and even in the monsoon systems of China and India. In the Mediterranean area, the biological and agronomical success of this species is due to its adaptability to the Mediterranean climatic conditions: mild, wet winters with temperatures that drop below 10 °C but rarely below 0 °C and warm, dry summers. When weather conditions become more extreme (drought, high, or low temperatures) or soil conditions are not optimal for olive growth (salinity, low oxygen, nutrient deficiencies), the plant can be subjected to abiotic stresses, which may have negative effects on its physiology. The damages derived from stresses caused by environmental constrains are often not immediately recognized in olive orchards, since plants are largely grown in non-specialized planting systems that are managed with limited cultural practices. However, due to the renewed interest in extra-virgin olive oil for its beneficial health effects, olive cultivation has now been modified from traditional low-density and low-input to high-density and high-input growing systems. Information on the effect of abiotic stresses on trees under the new cultivation systems is scarce due to the wide differences in management practices, environmental conditions and the increase in the use of selected varieties. Under these new conditions, the abiotic factors and their related stresses might have a strong impact on both yield and quality. In this chapter, we focus on physiological responses of olive trees to drought, salinity, and temperature stress. The reader can refer to the existing literature for other abiotic stresses.
Advanced analysis of developmental and ripening characteristics of pollinated common-type fig (Ficus carica L.)
, 98 - 106. Publisher's VersionAbstract
Development and ripening processes differ in pollinated and parthenocarpic fruit. While the facultative parthenocarpic common-type fig fruit serves as a receptacle for flower development, it becomes fleshy by either pollination or through a parthenocarpic process. Here we studied the effect of pollination on common-type fig fruit development and ripening characteristics compared to the parthenocarpic fruit under otherwise identical conditions. The effects of pollination on fruit development were investigated on the tree and in storage. Pollinated fruit showed altered developmental processes. Ripened pollinated fruit were round, in contrast to the pear-like shape of the parthenocarpic fruit. The pollinated fruit also had a larger diameter and weight and improved firmness compared to the parthenocarpic fruit. At harvest, the pollinated fruit exhibited more commercially desirable physical and taste characteristics, with advanced fertile nutlets compared to the sterile undeveloped non-bearing nutlets of the parthenocarpic fruit. During storage, senescence and spoilage of the pollinated fruit were slower than in parthenocarpic fruit, as manifested by firmness, internal texture, weight, size, shriveling, and decay. Thus, pollination of the common-type fig cultivar Brown Turkey delayed senescence and extended the shelf life of its fruit. The external and internal morphological differences throughout post-pollination development make common-type fig an excellent research tool for studies of physiological and molecular aspects of pollination.
Drought tolerance of three olive cultivars alternatively selected for rain fed or intensive cultivation
, 158 - 162. Publisher's VersionAbstract
Physiological drought response was evaluated for two olive cultivars commonly grown under rain fed conditions (‘Souri’ and ‘Picual’) and another selected for intensive, irrigated cultivation (‘Barnea’). ‘Souri’ is a traditional local Israeli cultivar, ‘Picual’ originated in Spain and ‘Barnea’ is a modern Israeli cultivar. Trees in pots were alternatively provided well irrigated conditions (100% FC, field capacity) or allowed to dry, first to 33% FC and then to 10% FC. Under conditions of greatest water availability, the ‘Barnea’ cultivar had the highest stomatal conductance and net photosynthesis, significantly higher than that found in ‘Souri’. Stomatal conductance and leaf water potential of ‘Souri’ and ‘Picual’ at 33% FC were not affected relative to the well irrigated treatment but decreased significantly at 10% FC. Photosynthetic parameters of ‘Souri' and ‘Picual’ were not affected by water stress. Stem growth was also not affected by drought in ‘Souri’ but was reduced at 10% FC in ‘Picual’. In contrast, the ‘Barnea’ showed higher sensitivity to low water availability with stomatal conductance and net photosynthesis reduced at 33% FC and sharp decreases in these and leaf water potential occurring at 10% FC. At 10% FC ‘Barnea’ trees showed stem shrinkage, a phenomenon not observed in the other cultivars. These results suggest a tradeoff between selection for suitability in intensively irrigated orchards and tolerance to drought.
Chlorophyll metabolism in pollinated vs. parthenocarpic fig fruits throughout development and ripening
, 491 - 504. Publisher's VersionAbstract
Expression of 13 genes encoding chlorophyll biosynthesis and degradation was evaluated. Chlorophyll degradation was differentially regulated in pollinated and parthenocarpic fig fruits, leading to earlier chlorophyll degradation in parthenocarpic fruits.
Inhibition of cytochrome P450 3A by acetoxylated analogues of resveratrol in in vitro and in silico models
31557. Publisher's VersionAbstract
Many dietary compounds, including resveratrol, are potent inhibitors of CYP3A4. Here we examined the potential to predict inhibition capacity of dietary polyphenolics using an in silico and in vitro approaches and synthetic model compounds. Mono, di and tri-acetoxy resveratrol were synthesized, a cell line of human intestine origin and microsomes from rat liver served to determine their in vitro inhibition of CYP3A4 and compared to that of resveratrol. Docking simulation served to predict the affinity of the synthetic model compounds to the enzyme. Modelling of the enzyme’s binding site revealed three types of interaction: hydrophobic, electrostatic and H-bonding. The simulation revealed that each of the examined acetylations of resveratrol led to the loss of important interactions of all types. Tri-acetoxy resveratrol was the weakest inhibitor in vitro despite being the more lipophilic and having the highest affinity for the binding site. The simulation demonstrated exclusion of all interactions between tri-acetoxy resveratrol and the heme due to distal binding, highlighting the complexity of the CYP3A4 binding site, which may allow simultaneous accommodation of two molecules. Finally, the use of computational modelling may serve as a quick predictive tool to identify potential harmful interactions between dietary compounds and prescribed drugs.
Tissue-Specific Transcriptome and Hormonal Regulation of Pollinated and Parthenocarpic Fig (Ficus carica L.) Fruit Suggest that Fruit Ripening Is Coordinated by the Reproductive Part of the Syconium
. Frontiers in Plant Science 2016
1696. Publisher's VersionAbstract
In the unconventional climacteric fig (Ficus carica) fruit, pollinated and parthenocarpic fruit of the same genotype exhibit different ripening characteristics. Integrative comparative analyses of tissue-specific transcript and of hormone levels during fruit repining from pollinated vs. parthenocarpic fig fruit were employed to unravel the similarities and differences in their regulatory processes during fruit repining. Assembling tissue-specific transcripts into 147,000 transcripts with 53,000 annotated genes provided new insights into the spatial distribution of many classes of regulatory and structural genes, including those related to color, taste and aroma, storage, protein degradation, seeds and embryos, chlorophyll, and hormones. Comparison of the pollinated and parthenocarpic tissues during fruit ripening showed differential gene expression, especially in the fruit inflorescence. The distinct physiological green phase II and ripening phase III differed significantly in their gene-transcript patterns in both pulp and inflorescence tissues. Gas chromatographic analysis of whole fruits enabled the first determination of ripening-related hormone levels from pollinated and non-pollinated figs. Ethylene and auxin both increased during fruit ripening, irrespective of pollination, whereas no production of active gibberellins or cytokinins was found in parthenocarpic or pollinated ripening fruit. Tissue-specific transcriptome revealed apparent different metabolic gene patterns for ethylene, auxin and ABA in pollinated vs. parthenocarpic fruit, mostly in the fruit inflorescence. Our results demonstrate that the production of abscisic acid (ABA), non-active ABA–GE conjugate and non-active indoleacetic acid (IAA)–Asp conjugate in pollinated fruits is much higher than in parthenocarpic fruits. We suggest that fruit ripening is coordinated by the reproductive part of the syconium and the differences in ABA production between pollinated and parthenocarpic fig fruit might be the key to their different ripening characteristics.