Isolation and developmental expression analysis of L-myo-inositol-1-phosphate synthase in four Actinidia species

Physiology and proteomics analyses reveal the response mechanisms of Rhizophora mucronata seedlings to prolonged complete submergence

Mangrove seedlings are subject to natural tidal inundation, while occasional flooding may lead to complete submergence. Complete submergence reduces light availability and limits gas exchange, affecting several plant metabolic processes. The present study focuses on Rhizophora mucronata, a common mangrove species found along the coasts of Thailand and the Malay Peninsula. To reveal response mechanisms of R. mucronata seedlings to submergence, a physiological investigation coupled with proteomic analyses of leaf and root tissues was carried out in plants subjected to 20 days of control (drained) or submerged conditions. Submerged seedlings showed decreased photosynthetic activity, lower stomatal conductance, higher total antioxidant capacity in leaves and higher lipid peroxidation in roots than control plants. At the same time, tissue nutrient ion content displayed organ-specific responses. Proteome analysis revealed a significant change in 240 proteins in the leaves and 212 proteins in the roots. In leaves, most differentially accumulated proteins (DAPs) are associated with nucleic acids, stress response, protein transport, signal transduction, development and photosynthesis. In roots, most DAPs are associated with protein metabolic process, response to abiotic stimulus, nucleic acid metabolism and transport. Our study provides a comprehensive understanding of submergence responses in R. mucronata seedlings. The results suggest that submergence induced multifaceted stresses related to light limitation, oxidative stress and osmotic stress, but the responses are organ specific. The results revealed many candidate proteins which may be essential for survival of R. mucronata under prolonged submergence.

Foliar Application of an Inositol-Based Plant Biostimulant Boosts Zinc Accumulation in Wheat Grains: A μ-X-Ray Fluorescence Case Study

There has been much interest in the incorporation of organic molecules or biostimulants into foliar fertilizers with the rationalization that these compounds will enhance the uptake, or subsequent mobility of the applied nutrient. The objective of this research was to investigate the effects of an inositol-based plant stimulant on the mobility and accumulation of foliar-applied zinc (Zn) in wheat plants (Triticum aestivum L.). High-resolution elemental imaging with micro-X-ray fluorescence (μ-XRF) was utilized to examine Zn distribution within the vascular bundle of the leaf and whole grains. The inclusion of myo-inositol with Zinc sulfate, significantly increased Zn concentration in shoots in contrast to untreated controls and Zn sulfate applied alone. Foliar Zn treated plants increased Zn in grains by 5-25% with myo-inositol plus Zn treated plants significantly increasing grain Zn concentration compared to both Zn treated and non-treated controls. XRF imaging revealed Zn enrichment in the bran layer and germ, with a very low Zn concentration present in the endosperm. Plants treated with Zn plus myo-inositol showed an enhanced and uniform distribution of Zn throughout the bran layer and germ with an increased concentration in the endosperm. While our data suggest that foliar application of myo-inositol in combination with Zn may be a promising strategy to increase the absorption and mobility of Zn in the plant tissue and subsequently to enhance Zn accumulation in grains, further research is needed to clarify the mechanisms by which myo-inositol affects plant metabolism and nutrient mobility.

Overexpression of MdMIPS1 enhances salt tolerance by improving osmosis, ion balance, and antioxidant activity in transgenic apple

Myo-inositol and its derivatives play vital roles in plant stress tolerance. Myo-inositol-1-phosphate synthase (MIPS) is the rate-limiting enzyme of myo-inositol biosynthesis. However, the role of apple MIPS-mediated myo-inositol biosynthesis in stress tolerance remains elusive. In this study, we found that ectopic expression of MdMIPS1 from apple increased myo-inositol content and enhanced tolerance to salt and osmotic stresses in transgenic Arabidopsis lines. In transgenic apple lines over-expressing MdMIPS1, the increased myo-inositol levels could promote accumulation of other osmoprotectants such as glucose, sucrose, galactose, and fructose, to alleviate salinity-induced osmotic stress. Also, it was shown that overexpression of MdMIPS1 enhanced salinity tolerance by improving the antioxidant system to scavenge ROS, as well as Na⁺ and K⁺ homeostasis. Taken together, our results revealed a protective role of MdMIPS1-mediated myo-inositol biosynthesis in salt tolerance by improving osmotic balance, antioxidant defense system, and ion homeostasis in apple.

A Cotton (Gossypium hirsutum) Myo-Inositol-1-Phosphate Synthase (GhMIPS1D) Gene Promotes Root Cell Elongation in Arabidopsis

Myo-inositol-1-phosphate synthase (MIPS, EC 5.5.1.4) plays important roles in plant growth and development, stress responses, and cellular signal transduction. MIPS genes were found preferably expressed during fiber cell initiation and early fast elongation in upland cotton (Gossypium hirsutum), however, current understanding of the function and regulatory mechanism of MIPS genes to involve in cotton fiber cell growth is limited. Here, by genome-wide analysis, we identified four GhMIPS genes anchoring onto four chromosomes in G. hirsutum and analyzed their phylogenetic relationship, evolutionary dynamics, gene structure and motif distribution, which indicates that MIPS genes are highly conserved from prokaryotes to green plants, with further exon-intron structure analysis showing more diverse in Brassicales plants. Of the four GhMIPS members, based on the significant accumulated expression of GhMIPS1D at the early stage of fiber fast elongating development, thereby, the GhMIPS1D was selected to investigate the function of participating in plant development and cell growth, with ectopic expression in the loss-of-function Arabidopsis mips1 mutants. The results showed that GhMIPS1D is a functional gene to fully compensate the abnormal phenotypes of the deformed cotyledon, dwarfed plants, increased inflorescence branches, and reduced primary root lengths in Arabidopsis mips1 mutants. Furthermore, shortened root cells were recovered and normal root cells were significantly promoted by ectopic expression of GhMIPS1D in Arabidopsis mips1 mutant and wild-type plants respectively. These results serve as a foundation for understanding the MIPS family genes in cotton, and suggest that GhMIPS1D may function as a positive regulator for plant cell elongation.

Exogenous myo-inositol alleviates salinity-induced stress in Malus hupehensis Rehd

Myo-inositol mediates various physiological processes and stress responses. Here, we investigated its role in Malus hupehensis Rehd. plants when grown hydroponically under saline conditions. Salt-stressed plants showed reduced growth and marked declines in photosynthetic activity and chlorophyll concentrations. However, pretreatment with 50 μM myo-inositol significantly alleviated those inhibitions and enabled plants to maintain their photosynthetic capacity. In addition to changing stomatal behavior, exogenous myo-inositol inhibited ROS accumulation and Na⁺ uptake. In contrast, activities of antioxidant systems were enhanced, and expression was elevated for genes involved in Na⁺ uptake (e.g., HKT1, NHX1, SOS1, and SOS2). This exogenous application also provoked the accumulation of sugars or sugar alcohols, which partially contributed to the maintenance of osmotic balance, and the scavenging of ROS, either directly or indirectly. In summary, myo-inositol appears to alleviate the salt-induced inhibition of physiological processes for M. hupehensis, not only by supporting the plant's antioxidant defense system but also by mediating Na⁺ and K⁺ homeostasis and the osmotic balance.

Overexpression of PeMIPS1 confers tolerance to salt and copper stresses by scavenging reactive oxygen species in transgenic poplar

Myo-inositol is a vital compound in plants. As the key rate-limiting enzyme in myo-inositol biosynthesis, l-myo-inositol-1-phosphate synthase (MIPS) is regarded as a determinant of the myo-inositol content in plants. The up-regulation of MIPS genes can increase the myo-inositol content, thereby enhancing the plant's resistance to a variety of stresses. However, there are few reports on the roles of myo-inositol and the identification of MIPS in woody trees. In this study, a MIPS gene, named as PeMIPS1, was characterized from Populus euphratica Oliv. The heterologous expression of PeMIPS1 compensated for inositol production in the yeast inositol auxotrophic mutant ino1 and the phenotypic lesions of the atmips1-2 mutant, an Arabidopsis MIPS1 knock-out mutant. A subcellular location analysis showed that the PeMIPS1-GFP fusion was localized in the nucleus and cytoplasm, but not in the chloroplasts, indicating that PeMIPS1 represented the cytosolic form of MIPS in P. euphratica. Interestingly, PeMIPS1 was not only inducible by drought and high salinity, but also by CuSO4 treatment. The transgenic poplar lines overexpressing PeMIPS1 had greater plant heights, shoot biomasses and survival rates than the wild type during the salt- or copper-stress treatment, and this was accompanied by an increase in the myo-inositol content. The overexpression of PeMIPS1 resulted in the increased activities of antioxidant enzymes and the accumulation of ascorbate, a key nonenzymatic antioxidant in plant, which partly accounted for the enhanced reactive oxygen species-scavenging capacity and the lowered hydrogen peroxide and malondialdehyde levels in the transgenic poplar. To the best of our knowledge, this study is the first to report the roles of MIPS genes in the tolerance to copper stress.

The Nutritional and Health Benefits of Kiwiberry (Actinidia arguta) - a Review

The kiwiberry (Actinidia arguta) is a new product on the market that is enjoying growing consumer acceptance around the world. This widespread interest has created increased demand for identification of the kiwiberry's nutritional health benefits. Containing over 20 essential nutrients and a range of vitamins, the kiwiberry comes near the top of fruits classed as superfoods. It is one of the richest sources of vitamin C with up to 430 mg/100 g fresh weight (FW) and is considered the richest dietary source of myo-inositol (up to 982 mg/100 g FW). The kiwiberry is also one of the richest sources of lutein (up to 0.93 mg/100 g FW) in commonly consumed fruit. Furthermore, containing up to 1301.1 mg/100 g FW phenolics and significant amounts of the essential minerals of potassium, calcium and zinc, the kiwiberry rates very highly as a 'healthy food'. The type and number of this fruit's medicinally promising nutrients have motivated ongoing investigations into its antioxidant, anti-tumour and anti-inflammatory properties. Early research has pointed to the kiwiberry being a very promising treatment for some cancers and health issues involving the gastrointestinal system, hypercholesterolemia and certain cancers. A pharmaceutical composition of A. arguta, A. kolomikta, and A. polygama extracts has already been registered for the prevention and treatment of some immune (inflammatory) mediated diseases, as well as the treatment of some non-allergic inflammatory diseases. This paper reviews and highlights the limited nutritional and therapeutic information currently available on the kiwiberry, a minor fruit possessing such major properties.