Selenium-Enriched Pollen Grains of Olea europaea L.: Ca2+ Signaling and Germination Under Oxidative Stress

Abstract

Selenium (Se) shows antioxidant properties that can be exploited in plants to combat abiotic stresses caused by reactive oxygen species produced in excess (ROS). Here, we show that the Se-fertilization of olive trees with sodium selenate effectively protects the pollen from oxidative stress. Pollen isolated from plants treated with Se or from untreated controls was incubated in vitro with H 2 O 2 to produce an oxidative challenge. Given the impact of ROS on Ca 2+ homeostasis and Ca 2+-dependent signaling, cytosolic Ca 2+ was measured to monitor cellular perturbations. We found that H 2 O 2 interrupted Ca 2+ homeostasis only in untreated pollen, while in samples treated in vitro with sodium selenate or selenium methionine, Ca 2+ homeostasis was preserved. Furthermore, germination rates were considerably better maintained in Se-fertilized pollen compared to non-fertilized pollen (30% vs. 15%, respectively) after exposure to 1 mM H 2 O 2. The same was observed with pollen treated in vitro with Se-methionine, which is the organic form of Se, in which part of the fertigated sodium selenate is converted in the plant. Combined, our results show a close correlation between ROS, Ca 2+ homeostasis, and pollen fertility and provide clear evidence that Se-fertilization is a potential approach to preserve or improve agricultural productivity.

Selective Inhibition of Wild Sunflower Reproduction with Mugwort Aqueous Extract, Tested on Cytosolic Ca2+ and Germination of the Pollen Grains

“…The link between cytosolic Ca 2+ and germination of the three sunflower pollen populations was in agreement with what was reported in our previous studies and in those of other authors [18,19,26,27].…”

Effects of Megafol on the Olive Cultivar ‘Arbequina’ Grown Under Severe Saline Stress in Terms of Physiological Traits, Oxidative Stress, Antioxidant Defenses, and Cytosolic Ca2+

“…The correlation observed between cytosolic Ca 2+ and germination highlighted in our previous work suggests that the germination capacity of pollen grains subjected to oxidative stress is linked to the maintenance of Ca 2+ homeostasis ( Del Pino et al, 2019a , b ). The novelty of the treatment with Meg was the ability of the biostimulant to block the bioavailability of the cytosolic ion, thus avoiding unwanted transduction of signals in saline stress ( Figure 4 ).…”

“…Cytosolic Ca 2+ levels were determined spectrofluorometrically using the probe FURA-2 AM ( Del Pino et al, 2019a , b ). Olive pollen (100 mg) from sub-samples stored in the dark at 5°C was suspended in 10 ml PBS and hydrated for 2 days at 25°C.…”

The First Evidence of the Beneficial Effects of Se-Supplementation on In Vitro Cultivated Olive Tree Explants

“…Particularly, in olive trees ( Olea europaea L.), several beneficial effects of Se administered as sodium selenate via foliar spray at a concentration of 100–150 mg L −1 in pots and field experiments and of 10–30 mg L −1 added to the nutrient solution in hydroponics have been reported. Some of the reported effects are: improved drought and salt stress tolerance [ 14 , 15 , 16 ], increased oil phenol content [ 17 , 18 ], better pollen germination [ 19 , 20 ], and increased Se content in fruits [ 21 , 22 ]. However, no studies have been done on the possible beneficial effects of Se on olive tree in vitro.…”