A Berberine Bridge Enzyme-Like Protein, GmBBE-like43, Confers Soybean's Coordinated Adaptation to Aluminum Toxicity and Phosphorus Deficiency.

Phosphorus (P) deficiency and aluminum (Al) toxicity often coexist and are two major limiting factors for crop production in acid soils. The purpose of this study was to characterize the function of GmBBE-like43, a berberine bridge enzyme-like protein-encoding gene, in soybean (Glycine max) adaptation to Al and low P stresses. Present quantitative real-time PCR (qRT-PCR) assays confirmed the phosphate (Pi)-starvation enhanced and Al-stress up-regulated expression pattern of GmBBE-like43 in soybean roots. Meanwhile, the expression of a GmBBE-like43-GFP chimera in both common bean hairy roots and tobacco leaves demonstrated its cell wall localization. Moreover, both transgenic Arabidopsis and soybean hairy roots revealed the function of GmBBE-like43 in promoting root growth under both Al and low P stresses. GmBBE-like43-overexpression also resulted in more H2O2 production on transgenic soybean hairy root surface with oligogalacturonides (OGs) application and antagonized the effects of Al on the expression of two SAUR-like genes. Taken together, our results suggest that GmBBE-like43 might be involved in the soybean's coordinated adaptation to Al toxicity and Pi starvation through modulation of OGs-oxidation in the cell wall.

Functional Characterization of Aluminum (Al)-Responsive Membrane-Bound NAC Transcription Factors in Soybean Roots.

The membrane-bound NAC transcription (NTL) factors have been demonstrated to participate in the regulation of plant development and the responses to multiple environmental stresses. This study is aimed to functionally characterize soybean NTL transcription factors in response to Al-toxicity, which is largely uncharacterized. The qRT-PCR assays in the present study found that thirteen out of fifteen GmNTL genes in the soybean genome were up-regulated by Al toxicity. However, among the Al-up-regulated GmNTLs selected from six duplicate gene pairs, only overexpressing GmNTL1, GmNTL4, and GmNTL10 could confer Arabidopsis Al resistance. Further comprehensive functional characterization of GmNTL4 showed that the expression of this gene in response to Al stress depended on root tissues, as well as the Al concentration and period of Al treatment. Overexpression of GmNTL4 conferred Al tolerance of transgenic Arabidopsis in long-term (48 and 72 h) Al treatments. Moreover, RNA-seq assay identified 517 DEGs regulated by GmNTL4 in Arabidopsis responsive to Al stress, which included MATEs, ALMTs, PMEs, and XTHs. These results suggest that the function of GmNTLs in Al responses is divergent, and GmNTL4 might confer Al resistance partially by regulating the expression of genes involved in organic acid efflux and cell wall modification.