A JAZ Protein in Astragalus sinicus Interacts with a Leghemoglobin through the TIFY Domain and Is Involved in Nodule Development and Nitrogen Fixation

Abstract

Leghemoglobins (Lbs) play an important role in legumes-rhizobia symbiosis. Lbs bind O2 and protect nitrogenase activity from damage by O2 in nodules, therefore, they are regarded as a marker of active nitrogen fixation in nodules. Additionally, Lbs are involved in the nitric oxide (NO) signaling pathway, acting as a NO scavenger during nodule development and nitrogen fixation. However, regulators responsible for Lb expression and modulation of Lb activity have not been characterized. In our previous work, a Jasmonate-Zim-domain (JAZ) protein interacting with a Lb (AsB2510) in Astragalus sinicus was identified and designated AsJAZ1. In this study, the interaction between AsJAZ1 and AsB2510 was verified using a yeast two-hybrid system and in vitro Glutathione S-transferase (GST) pull-down assays, resulting in identification of the interaction domain as a TIFY (previously known as zinc-finger protein expressed in inflorescence meristem, ZIM) domain. TIFY domain is named after the most conserved amino acids within the domain. Bimolecular fluorescence complementation (BiFC) was used to confirm the interaction between AsJAZ1 and AsB2510 in tobacco cells, demonstrating that AsJAZ1-AsB2510 interaction was localized to the cell membrane and cytoplasm. Furthermore, the expression patterns and the symbiotic phenotypes of AsJAZ1 were investigated. Knockdown of AsJAZ1 expression via RNA interference led to decreased number of nodules, abnormal development of bacteroids, accumulation of poly-x-hydroxybutyrate (PHB) and loss of nitrogenase activity. Taken together, our results suggest that AsJAZ1 interacts with AsB2510 and participates in nodule development and nitrogen fixation. Our results provide novel insights into the functions of Lbs or JAZ proteins during legume-rhizobia symbiosis.

Genome-wide identification and characterization of the TIFY gene family in kiwifruit

“…In addition, the TIFY gene family has several other functions. For example, AsJAZ1 in Astragalus sinicus was involved in nodule development and nitrogen fixation [ 22 ], and AhJAZ1 and AhTIFY8 in Arachis hypogaea also participated in the root nodule symbiosis process [ 23 ]. The multiple regulatory effects of the TIFY gene family in plant growth and stress resistance indicate that this family contains a large number of valuable gene resources related to plant life activities and stress resistance responses, and thus it is of great significance to mine, identify and characterize these genes.…”

Identification of TIFY Family Genes and Analysis of Their Expression Profiles in Response to Phytohormone Treatments and Melampsora larici-populina Infection in Poplar

“…Since JA is a key phytohormone in plant development, JAZ proteins were also found to play critical roles in the regulation of numerous aspects of plant development. In Astragalus sinicus , AsJAZ1 was found to interact with AsB2510 and participated in nodule development and nitrogen fixation (Li et al, 2015). In Arabidopsis, deletion of the two PPD genes (at the same locus) increased leaf lamina size and resulted in dome-shaped rather than flat leaves.…”

Comprehensive Analysis of the TIFY Gene Family and Its Expression Profiles under Phytohormone Treatment and Abiotic Stresses in Roots of Populus trichocarpa

“…Overexpression of ZmJAZ14 in Arabidopsis enhanced the plants' tolerance to JA and ABA treatments [14]. Additionally, AsJAZ1 can be involved in nodule development and nitrogen fixation by interacting with AsB2510 in Astragalus sinicus [15]. The PPD genes regulate tissue growth, modify lamina size, and restrict curvature of the leaf blade [16].…”