Selenium maintains cytosolic Ca2+ homeostasis and preserves germination rates of maize pollen under H2O2-induced oxidative stress

Abstract

Selenium (Se) displays antioxidant properties that can be exploited, in plants, to counteract abiotic stresses caused by overly-produced reactive oxygen species (ROS). Here, we show that fertigation of maize crops with sodium selenate effectively protects pollen against oxidative stress. Pollen isolated from Se-treated plants (Se1) and untreated controls (Se0) was incubated in vitro with H2O2 to produce oxidative challenge. Given the impact of ROS on Ca2+ homeostasis and Ca2+-dependent signaling, cytosolic Ca2+ was measured to monitor cellular perturbations. We found that H2O2 disrupted Ca2+ homeostasis in Se0 pollen only, while Se1 samples were preserved. The same trend was observed when Se0 samples were treated with sodium selenate or Se-methionine, which recapitulated in vitro the protective capacity of Se-fertigation. Furthermore, we found that germination rates were much better retained in Se1 as compared to Se0 (46% vs 8%, respectively) after exposure to 20 mM H2O2. The same was observed with Se0 pollen treated with Se-methionine, which is the organic form of Se into which most fertigated sodium selenate converts in the plant. These results, together, show a close correlation between ROS, Ca2+ homeostasis and pollen fertility, and provide strong evidence that Se-fertigation is an excellent approach to preserve or enhance 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.…”

Persistence of the Effects of Se-Fertilization in Olive Trees over Time, Monitored with the Cytosolic Ca2+ and with the Germination of Pollen

“…ROS become toxic at high concentrations, induce oxidative stress and deregulate molecular signals including cytosolic Ca 2+ [20][21][22][23][24]. Several studies conducted on the cytosolic Ca 2+ of olive pollen, among the molecular signalling networks, resulted in a reliable experimental model [25,26]. The levels of Ca 2+ are closely related to the cytosolic concentration of the ions, which changes over time are possible to trace through the marking of pollen with the FURA-2AM probe [25][26][27].…”

“…Several studies conducted on the cytosolic Ca 2+ of olive pollen, among the molecular signalling networks, resulted in a reliable experimental model [25,26]. The levels of Ca 2+ are closely related to the cytosolic concentration of the ions, which changes over time are possible to trace through the marking of pollen with the FURA-2AM probe [25][26][27]. Furthermore, the fluctuations of cytosolic Ca 2+ have an important role in the germination of pollen and in the growth of the pollen tube, even if up to now the interactions between the two events are little known.…”