Hydrogen sulfide promotes nodulation and nitrogen fixation in soybean-rhizobia symbiotic system

Abstract

The rhizobium-legume symbiotic system is crucial for nitrogen cycle balance in agriculture. Hydrogen sulfide (H2S), a gaseous signaling molecule, may regulate various physiological processes in plants. However, whether H2S has regulatory effect in this symbiotic system remains unknown. Herein, we investigated the possible role of H2S in the symbiosis between soybean (Glycine max) and rhizobium (Sinorhizobium fredii). Our results demonstrated that exogenous H2S donor (sodium hydrosulfide, NaHS) treatment promoted soybean growth, nodulation and nitrogenase (Nase) activity. Western blotting analysis revealed that the abundance of nitrogenase component nifH was increased by NaHS treatment in nodules. Quantitative real-time PCR data showed that NaHS treatment up-regulated the expressions of symbiosis-related genes nodC and nodD of S. fredii. Besides, expression of soybean nodulation marker genes including early nodulin 40 (GmENOD40), ERF required for nodulation (GmERN), nodulation signaling pathway2b (GmNSP2b) and nodulation inception genes (GmNIN1a, GmNIN2a and GmNIN2b) were up-regulated. Moreover, the expressions of glutamate synthase (GmGS), nitrite reductase (GmNiR), ammonia transporter (GmSAT1), and nifH involved in nitrogen metabolism were up-regulated in NaHS-treated soybean roots and nodules. Together, our results suggested that H2S may act as a positive signaling molecule in soybean-rhizobia symbiotic system and enhance their nitrogen fixation ability.HighlightWe demonstrated for the first time that H2S as a signaling molecule may promote the establishment of symbiotic relationship and nitrogen fixation ability in the soybean-rhizobia symbiotic system.

Hydrogen sulfide and rhizobia synergistically regulate nitrogen (N) assimilation and remobilization during N deficiency‐induced senescence in soybean

“…Additionally, H 2 S significantly enhanced the content of ARA and Lb in nodules in rhizobia‐inoculated plants (Figure f,g), indicating that H 2 S promoted N metabolism and remobilization of symbiotic systems by enhancing the N fixation capacity of nodules. This was consistent with our previous findings that H 2 S effectively facilitated the nodulation and N fixation of the soybean‐rhizobia symbiotic system (Zou et al, ). As is well known, Rubisco is crucial for photosynthesis (Bloom & Lancaster, ).…”

“…After the first true leaves of the plants were fully expanded, some plants were inoculated with rhizobia ( Sinorhizobium fredii Q8 strain), by the addition of 10‐ml of a rhizobia suspension (OD 600 = 0.05) to each bag. Thereafter, some seedlings were watered with 10‐ml of 100‐μM NaHS solution every 3 days (Zou et al, ), and blank controls were watered with sterilized distilled water. Additionally, 50‐ml of sterile N‐free nutrient solution was added to each bag every week to maintain constant humidity and nutrition.…”

“…Nitrogenase activity was measured by acetylene reduction assay (ARA) in nodules on the 26th day (Wych & Rains, ; Zou et al, ). Fresh root nodules (0.2 g) were weighed into a 25‐ml vial, and 200‐μl of acetylene was added.…”

“…Moreover, we recently demonstrated that H 2 S was of the utmost importance in soybean seedlings for its ability to improve the plant biomass and cause the accumulation of nutrients such as Fe and N under conditions of iron deficiency (Chen et al, ). Moreover, the nodulation and N fixation capacity of the soybean symbiotic system were reinforced by the action of H 2 S (Zou et al, ).…”

Revealing on hydrogen sulfide and nitric oxide signals co‐ordination for plant growth under stress conditions

“…A rapid increase in H 2 S and NO has been recorded in shoot tips of sweet potato seedlings exposed to NaHS (Zhang et al ). Similar results have been recorded in willow shoots and seedlings of soybean (Zou et al ). These results signify that H 2 S triggers adventitious root formation via stimulating the upstream process of NO and IAA transduction signaling pathways (Zhang et al ).…”