Up-regulation of a stress-responsive endochitinase VvChit-IV in grapevine cell cultures improves in vitro stress tolerance

Chitinases are pathogenesis-related proteins, which play an important role in plant growth regulation, defense mechanism, and stress tolerance. Embryogenic cultures from Vitis vinifera cv. Tempranillo exposed to in vitro stress exhibited the expression of an extracellular class IV endochitinase VvChit-IV. Phylogenetic and conserved motif analyses provided insights into the evolutionary relationships of chitinases. A computation-based investigation showed conserved domains and illustrated a chitin-binding site for chitin cleavage with a catalytic domain of glycoside hydrolase. Interestingly, gene expression pattern showed a differential expression of VvChit-IV associated with embryonic stress response to in vitro conditions. In response to in vitro stress, transcript level of VvChit-IV increased in embryogenic calli and cell suspensions and peaked at 1.5 and 3 folds, respectively, when compared to an internal reference gene. Evidence of tissue culture stress-induced endochitinase was reported here for the first time indicating that in vitro stress could mitigate elicitor application to induce chitinase expression and can stimulate an immune response against abiotic constraints. Data showed that up-regulation of VvChit-IV was associated with a substantial increase of H₂O₂ and proline without significant change in malondialdehyde content suggesting that the H₂O₂ signaling network might trigger a priming effect to boost the defense response against environmental stress. Endochitinase activation in plant stress mitigation was thus highlighted to improve tolerance through attenuation of oxidative stress. This study revealed that the grapevine endochitinase is promising for enhancing coping-oriented adaptation and abiotic stress tolerance, which gives new insights into its feasibility for use in cross-tolerance and crop improvement.

Old Catharanthus roseus culture (14 years) produced somatic embryos and plants and showed normal genome size; demonstrated an increased antioxidant defense mechanism; and synthesized stress proteins as biochemical, proteomics, and flow-cytometry studies reveal

Various strategies have been developed globally to conserve germplasm by propagating plants. One important technique is in vitro propagation and preservation through tissue culture. In many investigated plants, the long in vitro conservation is plagued with several limitations like genetic variations, developmental errors in cells or tissues due to induced stress. This provoked us to conduct a study of Catharanthus roseus culture maintained for over fourteen long years and a newly established 8-month-old culture. The present study investigated and compared the two tissue types differing by their age. The biomass accumulation, the biochemical differences of the two, dead cell analysis with aging via confocal microscopy, and liquid chromatography-mass spectroscopy (LC-MS)-based proteomic differences were studied in old and newly established Catharanthus culture. The proteomic study reveals more than 120 upregulated or high abundance proteins in old culture as compared to newly established Catharanthus. The identified upregulated proteins are stress protein 69, heat shock proteins (HSP), isocitrate dehydrogenase, pyruvate dehydrogenase, and others. These proteins had an association with antioxidant activities, related to stress, and a few are linked to respiration. Our study reveals the presence of a robust antioxidant defense mechanism, i.e., 51.94%, 78.8%, and 61% higher SOD, APX, and CAT activities in older cultures (O) as compared to newly established tissues (N), which perhaps act against stress and may play a key role in ameliorating negative impacts of long-term in vitro conditions. The inherent strong antioxidant defense system in old cultures added resilience and enabled the culture to revive growth quickly (within 1-2 days) following transfer to new medium as compared to new culture (7-10 days). The biomass accumulation was more (37.08 %) in old tissues as compared to new culture. The 2C DNA or genome size of C. roseus especially the 14-year-old culture-derived regenerated plant was measured by flow cytometry. The 2C DNA size of this Catharanthus (old culture) plant is 1.516 pg, which is very similar to new culture-derived plants' and field-grown plants' genome size. No anomaly in genome size was noted in plants of old culture, as opposed to common perception.

In Vitro Assessment of Abiotic Stress in Date Palm: Salinity and Drought

Date palm is one of the major crops growing in regions where abiotic stress conditions are extreme. Abiotic stress affects plant growth, development, physiology, and biochemical processes. This chapter describes a protocol to evaluate the response of date palm cultures to abiotic stresses. Tolerance to salinity stress is assessed using calcium chloride (CaCl₂), potassium chloride (KCl), and sodium chloride (NaCl) at 11.96, 12.06, and 9.45 g/L, respectively (equivalent to 0.8 MPa osmotic potential), with different exposure durations (1-12 days). Polyethylene glycol (PEG 8000) is tested at 0-30% (w/v) to assess tolerance to drought stress. Techniques are described to define the effects of these stress agents on the growth of callus and cell suspension cultures, water content, proline accumulation, and Na⁺ and K⁺ content ratio, in addition to the technique used for determining the median lethal dose (LD₅₀) for PEG (29.5%) and NaCl (11.54 g/L). This protocol will be useful for future studies of in vitro selection of tolerant cell lines.