Excited to announce my first first-author publication (ever!) from my PhD is now online!!!! Co-first author with the amazing @Rafiqi51. Directed by @ehab_abouheif The Great @AbouheifLab. @BioMcGill @mcgillu @EvoDevoPanAm Want to know more? [A THREAD]
https://www.nature.com/articles/s41586-020-2653-6 1/n

We sought to understand the origin and elaboration of the #obligate #endosymbiosis between the #bacteria #Blochmannia and the #ant tribe #Camponotini #MajorEvolutionaryTransitions #EcoEvoDevo. @evodevo_papers @the_Node @Dev_Bio_Journal @MyrmecolNews 2/n

Developmental biology textbooks were of no use when the #segmentationhierarchy was #shook with #hoxgenes unleashed and the #fusion of highly conserved gene regulatory networks! #2germlines and an #embryo that gives humpty dumpty a run for his money. #CamponotusFloridanus 3/n

We found the developmental integration of Blochmannia into the Camponotini resulted in #radicalalterations in #embryogenesis, including the formation of the #germdisc at the anterior pole, #innovations in ant #development #bacteriocytes, and a new cell type: #germlinecapsule. 4/n

We show that during its vertical transmission, Blochmannia localize toward the posterior pole of the Camponotus floridanus oocyte, where it surrounds #germplasm. Germplasm (in flies, wasps, and ants) has a dual role of specifying the #germcells and the #abdomen of the embryo. 5/n

Surprisingly, we found as the #Cfloridanus oocyte transitions into an embryo, the number of #subcellular localization zones of #mRNAs and #proteins of #germplasm genes, increase from 1 to 4! Unlike flies and wasps, localization of these genes is combinatorial and dynamic. 6/n

Moreover, rather than simultaneously specifying #germcells and #embryonicposterior, the 4 zones of germline genes have distinct functions and a division of labor between them! Zone 1a and b regulate the localization of #Blochmannia into #Bacteriocytes. 7/n

Zone 2 is the #novelgermline that gives rise to the gonad. Zone 3 is expressed in the #germdisc and patterns the #embryo in the anterior, away from Blochmannia at the posterior pole. Zone 4 is expressed in the lining of the yolk sac and guides bacteriocytes into the midgut. 8/n

On top of this #germlinenetwork extravaganza, we discovered that in C. floridanus #inHoxweTrust abdA and Ubx are #maternally inherited, IN GERMPLASM! These Hox genes co-localized to the same 4 zones as the germline genes! All, while maintaining their role is segmentation. 9/n

Instead of #homeotic transformations #RNAi of abdA and Ubx resulted in truncation of the embryonic abdominal segments, phenocopying the #posteriorgroup mutants described by @REMLehmann. qPCR of this phenotype uncovered that abda and Ubx are upstream of the germline genes. 10/n

In addition to the truncation phenotype, RNAi of #abdA and #Ubx affected the products of the 4 zones that underlie the #radicalalterations including the complete loss or mislocalization of the #Bacteriome. But nothing is more striking than the #zipper phenotype observed. 11/n

To understand what role #Blochmannia has in establishing and regulating the 4 zones of Hox and germline gene expression, we treated C. floridanus colonies with #rifampicin, an antibiotic that eliminates Blochmannia from the colony. 12/n

We found Blochmannia selectively regulates localization and expression of Hox and germline genes. Blochmannia induces Z1b which patterns #Blochmannia into #Bacteriocytes and Z2 #novelgermline thereby inducing its own localization and vertical transmission #NicheConstruction. 13/n

We then transplanted #Blochmannia from wildtype embryos into Blochmannia-free embryos and rescued lost germline gene expression #oskar!!! Solidifying that #Blochmannia regulates the combination of Hox/germline genes within each zone like a #TranscriptionFactor. 14/n

Finally, we wanted to determine how the developmental integration of #Blochmannia into #Camponotini evolved. Our data suggested Blochmannia drove these developmental innovations at the origin of the #obligatesymbiosis. To test this, we performed an ancestral reconstruction. 15/n

The common ancestor of #dolichoderinae #myrmicinae and #formicinae forms its germdisc in the posterior, has a single zone of germline gene expression and no #maternalhox expression. Surprisingly #Brachymymrex an early branching #formicine forms its germdisc in the anterior! 16/n

Moreover the #Brachymyrmex germline forms outside the developing embryo and only reconnects during germband extension, similar to C. floridanus! There was a developmental capacity to separate embryonic posterior and germline functions of #germplasm! 17/n

Shockingly we found that one of the closest sister genera of Camponotini #gigantiops, as well as #oecophylla #anoplolepis and #formica have both a novel Zone of germline expression and #maternalhox localization. Using #oskar we determined this Zone is homologous to Zone 3! 18/n

This is the first timepoint of co-expression of Hox and germline genes and may have facilitated #rewiring of #segmentation hierarchy. Remarkably this interaction evolved first in somatic tissue, as #abdA #Ubx only localize in germplasm at the origin of the obligate symbiosis 19/n

At the #origin of obligate symbiosis between Blochmannia and Camponotini #Hox genes evolve in #germline #Zone1 #Zone4. Zone 1 patterns Bacteriocytes and Zone 4 guides Bacteriocytes form the #Bacteriome. Therefore #MaternalHox was essential for #developmental #integration. 20/n

These results support gradual #developmental #evolution toward the origin of #MajorTransition #obligatesymbiosis. Zones of germline gene expression increased from 1 -> 2 -> 3 -> 4 and #MaternalHox from 0 -> 1 -> 3 -> 4. Zones established a #coordinatesystem for patterning. 21/n

Other #MajorEvolutionaryTransitions may also require convergence of pre-existing #molecularcapacities and #ecologicalinteractions - as well as #fusion and #rewiring of #developmentalGRNs for their origin and developmental integration. #multicellularity #eusociality. END