Hydrogen Sulfide Alleviates Aluminum Toxicity via Decreasing Apoplast and Symplast Al Contents in Rice

Abstract

Hydrogen sulfide (H2S) plays a vital role in Al3+ stress resistance in plants, but the underlying mechanism is unclear. In the present study, pretreatment with 2 μM of the H2S donor NaHS significantly alleviated the inhibition of root elongation caused by Al toxicity in rice roots, which was accompanied by a decrease in Al contents in root tips under 50 μM Al3+ treatment. NaHS pretreatment decreased the negative charge in cell walls by reducing the activity of pectin methylesterase and decreasing the pectin and hemicellulose contents in rice roots. This treatment also masked Al-binding sites in the cell wall by upregulating the expression of OsSATR1 and OsSTAR2 in roots and reduced Al binding in the cell wall by stimulating the expression of the citrate acid exudation gene OsFRDL4 and increasing the secretion of citrate acid. In addition, NaHS pretreatment decreased the symplasmic Al content by downregulating the expression of OsNRAT1, and increasing the translocation of cytoplasmic Al to the vacuole via upregulating the expression of OsALS1. The increment of antioxidant enzyme [superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD)] activity with NaHS pretreatment significantly decreased the MDA and H2O2 content in rice roots, thereby reducing the damage of Al3+ toxicity on membrane integrity in rice. H2S exhibits crosstalk with nitric oxide (NO) in response to Al toxicity, and through reducing NO content in root tips to alleviate Al toxicity. Together, this study establishes that H2S alleviates Al toxicity by decreasing the Al content in the apoplast and symplast of rice roots.

Glutathione and hydrogen sulfide are required for sulfur‐mediated mitigation of Cr(VI) toxicity in tomato, pea and brinjal seedlings

“…In the Cr(VI) + S + BSO combination, endogenous H 2 S and cysteine contents and DES activity were not significantly affected while growth was suppressed more than Cr(VI) treatment alone (Table , Figs and ), whereas in Cr(VI) + S + BSO + GSH combination growth was much better than Cr(VI) treatment alone suggesting that H 2 S signaling preceded GSH biosynthesis and also essential for additional S‐mediated mitigation of Cr(VI) toxicity in tomato, pea and brinjal seedlings. Although H 2 S‐mediated mitigation of abiotic stress such as toxic metals in plants is now increasingly being known (Singh et al , Zhu et al , Kabała et al , Valivand et al ), its implication in essential element such as S‐mediated mitigation of Cr(VI) toxicity in plants was not known.…”

“…whereas in Cr(VI) + S + BSO + GSH combination growth was much better than Cr(VI) treatment alone suggesting that H 2 S signaling preceded GSH biosynthesis and also essential for additional S-mediated mitigation of Cr(VI) toxicity in tomato, pea and brinjal seedlings. Although H 2 S-mediated mitigation of abiotic stress such as toxic metals in plants is now increasingly being known (Singh et al 2015, Zhu et al 2018, Kabała et al 2019, Valivand et al 2019, its implication in essential element such as S-mediated mitigation of Cr(VI) toxicity in plants was not known. Toxic metals such as Cr(VI) has the capability of inducing generation of ROS which damage macromolecules (Kováčik et al 2013, Eleftheriou et al 2015, Singh et al 2015, Singh and Prasad 2019 and this tendency of Cr(VI) may indirectly be linked with sacrificed growth of studied vegetables (Table 1, Figs 5-10).…”

“…Besides this, in recent years, hydrogen sulfide (H 2 S), a colorless gaseous signaling molecule, has gained much attention because of its implication in regulating wide ranges of plant physiological processes (Hancock and Whiteman 2016, Corpas et al 2019, Kabała et al 2019. Reports of the metal toxicity alleviatory role of H 2 S under abiotic stress have increased (Singh et al 2015, Zhu et al 2018, Kabała et al 2019, Valivand et al 2019. However, implication of H 2 S signaling in regulating essential elements like S-mediated mitigation of Cr(VI) toxicity in plants, to our knowledge, is still not known.…”

Boron alters carboxyl group binding capacity and Al transport pathway to relieve Al toxicity

“…5a-c), meanwhile, the PME expression associated with PME activity were down-regulated by B application under Al stress conditions (Fig. 7a), indicating that B crosslinking with the ASP and promoted Al immobilization in pectins with a higher DM by reducing PME activity, and then decreased the Al enrichment in CW (Zhu et al , 2018). More importantly, B reduced the absorption peak strength at 1731 cm -1 (characteristic of the C=O stretching vibration from -COOR in pectin) (Fig.…”

“…Plants have developed a variety of detoxification strategies to cope with Al toxicity. These include shielding the CW of Al-binding site (Yan et al , 2018a), reducing the transfer of Al from the external environment to cells and detoxifying Al inside the apoplast (Zhu et al ., 2018), and compartmentalizes Al into the vacuoles (Xia et al ., 2010). Therefore, enhancing the exclusion of Al from root CW is the pivotal role of plants to resist Al toxicity (Zhu et al ., 2019).…”