Three classes of hemoglobins are required for optimal vegetative and reproductive growth of Lotus japonicus: genetic and biochemical characterization of LjGlb2-1. (13th August 2021)

• Record Type: Journal Article
• Authors: Villar, Irene; Rubio, Maria C; Calvo-Begueria, Laura; Pérez-Rontomé, Carmen; Larrainzar, Estibaliz; Wilson, Michael T; Sandal, Niels; Mur, Luis A; Wang, Longlong; Reeder, Brandon; Duanmu, Deqiang; Uchiumi, Toshiki; Stougaard, Jens; Becana, Manuel
• Editors: Napier, Richard
• Is Part Of: Journal of experimental botany. Volume 72:Number 22(2021)
• Page Start: 7778
• Page End: 7791
• Publication Date: 2021-08-13
• Subjects: Hemoglobins -- Lotus japonicus -- Medicago truncatula -- mutants -- nitric oxide -- symbiosis; Botany -- Periodicals; Botany, Experimental -- Periodicals; Plant physiology -- Periodicals; 580
• DOI: 10.1093/jxb/erab376
• Languages: English
• ISSNs: 0022-0957

Abstract

Abstract: Legumes express two major types of hemoglobins, namely symbiotic (leghemoglobins) and non-symbiotic (phytoglobins), with the latter being categorized into three classes according to phylogeny and biochemistry. Using knockout mutants, we show that all three phytoglobin classes are required for optimal vegetative and reproductive development of Lotus japonicus . The mutants of two class 1 phytoglobins showed different phenotypes: Ljglb1-1 plants were smaller and had relatively more pods, whereas Ljglb1-2 plants had no distinctive vegetative phenotype and produced relatively fewer pods. Non-nodulated plants lacking LjGlb2-1 showed delayed growth and alterations in the leaf metabolome linked to amino acid processing, fermentative and respiratory pathways, and hormonal balance. The leaves of mutant plants accumulated salicylic acid and contained relatively less methyl jasmonic acid, suggesting crosstalk between LjGlb2-1 and the signaling pathways of both hormones. Based on the expression of LjGlb2-1 in leaves, the alterations of flowering and fruiting of nodulated Ljglb2-1 plants, the developmental and biochemical phenotypes of the mutant fed on ammonium nitrate, and the heme coordination and reactivity of the protein toward nitric oxide, we conclude that LjGlb2-1 is not a leghemoglobin but an unusual class 2 phytoglobin. For comparison, we have also characterized a close relative of LjGlb2-1 in Medicago truncatula, MtLb3, and conclude that this is an atypical leghemoglobin. Abstract : Knockout mutants of Lotus japonicus demonstrate that three classes of phytoglobins are required for optimal vegetative and reproductive development. The most unusual hemoglobin LjGlb2-1 is genetically and biochemically characterized.