Oxylipin signaling in salt-stressed soybean is modulated by ligand-dependent interaction of Class II acyl-CoA-binding proteins with lipoxygenase

Abstract

Plant lipoxygenases (LOXs) oxygenate linoleic and linolenic acids, creating hydroperoxy derivatives, and from these, jasmonates and other oxylipins are derived. Despite the importance of oxylipin signaling, its activation mechanism remains largely unknown. Here, we show that soybean ACBP3 and ACBP4, two Class II acyl-CoA-binding proteins, suppressed activity of the vegetative LOX homolog VLXB by sequestering it at the endoplasmic reticulum. The ACBP4–VLXB interaction was facilitated by linoleoyl-CoA and linolenoyl-CoA, which competed with phosphatidic acid (PA) for ACBP4 binding. In salt-stressed roots, alternative splicing produced ACBP variants incapable of VLXB interaction. Overexpression of the variants enhanced LOX activity and salt tolerance in Arabidopsis and soybean hairy roots, whereas overexpressors of the native forms exhibited reciprocal phenotypes. Consistently, the differential alternative splicing pattern in two soybean genotypes coincided with their difference in salt-induced lipid peroxidation. Salt-treated soybean roots were enriched in C32:0-PA species that showed high affinity to Class II ACBPs. We conclude that PA signaling and alternative splicing suppress ligand-dependent interaction of Class II ACBPs with VLXB, thereby triggering lipid peroxidation during salt stress. Hence, our findings unveil a dual mechanism that initiates the onset of oxylipin signaling in the salinity response.

Genome-wide identification of acyl-CoA binding proteins and possible functional prediction in legumes

“…Besides, MeJA responsive elements (TGACG-motif and CGTCA-motif), abscisic acid-responsive (ABRE), and anaerobic induction elements (ARE and GC-motif) also were the rich types in the different subgroups ( Figure 4B ), suggesting that most ACBPs gene members were involved in related signaling pathways. These observations are consistent with previous reports ( Lung and Chye, 2019 ; Lung et al, 2021 ). Unlike the other subgroups, class I had no cell cycle regulation elements.…”

“…Therefore, it was speculated that ACBPs genes in Arachis hypogaea and Glycine max were more likely to be differentiated. This was consistent with reports of ACBPs function in Glycine max ( Azlan et al, 2021 ; Lung et al, 2021 ).…”

“…ACBPs have been identified in about 13 plant species ( Lung and Chye, 2016b ; Lung and Chye, 2016b ; Du et al, 2016 ; Lai and Chye, 2021 ). However, except for Soybean ( Glycine max ; Azlan et al, 2021 ; Lung et al, 2021 ), the characterization of other legumes ACBPs had remained unreported, even though these legumes are a globally crucial commercial crop cultivated for vegetables, oil crops, high protein crops, and plays a significant role in the food and chemical industries. Therefore, ACBPs exhibited diversity in structure and function by analyzing phylogenetic, gene structure and conserved motif, chromosomal distribution, homology, protein subcellular localization, cis-acting elements, and interaction protein, which is significant to further explore the gene function of ACBPs in these legumes.…”

“…AtACBP2 and AtACBP4 interact with AtEBP ( Ethylene-Responsive Element Binding Protein ), which activating the gene expression for downstream ethylene responses upon perceiving stress stimuli ( Li et al, 2008 ). Soybean class II acyl-CoA-binding proteins with lipoxygenase can modulate oxylipin signaling in salt-stressed ( Lung et al, 2021 ). These revealed that ACBPs have great value in biological function.…”

“…However, AtACBP4 and AtACBP5 (class IV) are nuclear or cytosol proteins involved in seed oil biosynthesis, seed germination, seedling development, pollen development, and cuticle formation ( Lung and Chye, 2016a ). Soybean ACBP3 and ACBP4 , two Class II acyl-CoA-binding proteins, regulate oxylipin signaling during salt stress ( Lung et al, 2021 ), but class II in Arabidopsis relate to heavy metal stress, freezing, hypoxia stress, embryogenesis, seed dormancy, germination, seedling development, stem cuticle formation ( Du et al, 2016 ). Concurrently, AtACBP1 , AtACBP2 , AtACBP4 , AtACBP5, and AtACBP6 had the same function as seed development, germination, and seedling development ( Lung and Chye, 2016a ; Du et al, 2016 ).…”