02682naa a2200445 a 450000100080000000500110000800800410001902200140006002400730007410000200014724501320016726000090029952014390030865000140174765000220176165000150178365000140179865300210181265300180183370000220185170000140187370000210188770000160190870000240192470000170194870000140196570000140197970000180199370000180201170000190202970000200204870000190206870000130208770000190210070000180211970000150213770000180215270000170217077300490218721469502022-09-29       2022    bl uuuu     u00u1 u    #d  a1469-81377 ahttps://doi-org.ez103.periodicos.capes.gov.br/10.1111/nph.183212DOI1 aFARIA, S. M. de  aThe innovation of the symbiosome has enhanced theevolutionary stability of nitrogen fixation in legumes.h[electronic resource]  c2022  aNitrogen-fixing symbiosis is globally important in ecosystem functioning and agriculture,yet the evolutionary history of nodulation remains the focus of considerable debate. Recentevidence suggesting a single origin of nodulation followed by massive parallel evolutionarylosses raises questions about why a few lineages in the N2-fixing clade retained nodulationand diversified as stable nodulators, while most did not. Within legumes, nodulation isrestricted to the two most diverse subfamilies, Papilionoideae and Caesalpinioideae, whichshow stable retention of nodulation across their core clades.We characterize two nodule anatomy types across 128 species in 56 of the 152 genera ofthe legume subfamily Caesalpinioideae: fixation thread nodules (FTs), where nitrogen-fixingbacteroids are retained within the apoplast in modified infection threads, and symbiosomes,where rhizobia are symplastically internalized in the host cell cytoplasm within membrane-bound symbiosomes (SYMs).Using a robust phylogenomic tree based on 997 genes from 147 Caesalpinioideae genera,we show that losses of nodulation are more prevalent in lineages with FTs than those withSYMs.We propose that evolution of the symbiosome allows for a more intimate and enduringsymbiosis through tighter compartmentalization of their rhizobial microsymbionts, resulting ingreater evolutionary stability of nodulation across this species-rich pantropical legume clade.  aEvolution  aNitrogen fixation  aNodulation  aSymbiosis  aFixation threads  aPhylogenomics1 aRINGELBERG, J. J.1 aGROSS, E.1 aKoenen, E. J. M.1 aCARDOSO, D.1 aAMETSITSI, G. K. P.1 aAKOMATEY, J.1 aMALUKM M.1 aNISHA, T.1 aGEHLOT, H. S.1 aWRIGHT, K. W.1 aTEAUMROONG, N.1 aSONGWATTANA, P.1 aLIMA, H. C. de1 aPRIN, Y.1 aZARTMAN, C. E.1 aSPRENT, J. I.1 aARDLEY, J.1 aHUGHES, C. E.1 aJAMES, E. K.  tNew Phytologistgv. 235, p. 2365-2377, 2022.