ABSTRACT
We undertook divergent selection experiments (Saclay DSEs) to investigate the genetic bases of phenotypic evolution in two inbred maize inbred lines, F252 and MBS847. The selected trait was flowering time. After 13 generations of selection, we obtained five distinct populations with a time-lag of roughly two weeks between Early- and Late/VeryLate-flowering populations. We used this unique material to characterize the genome-wide transcriptomic response to selection in the shoot apical meristem before, during and after floral transition in realistic field conditions during two consecutive years. We validated the reliability of performing RNA-sequencing in uncontrolled conditions. We found that roughly half of maize genes were expressed in the SAM, 59.3% of which were differentially expressed. We detected differential expression across meristem status, but also retrieved a subset of 2,451 genes involved in the response to selection. Among these, 22 genes displayed known function in maize flowering time. Furthermore, they were more often shared between inbreds than expected by chance, suggesting convergence of gene expression. We discuss new insights into the expression pattern of key players of the underlying gene regulatory network including ZCN8, RAP2.7, ZMM4, KN1, GA2ox1.
One sentence summary Experimental evolution in maize inbred lines uncovers determinants of the response to selection and convergence of gene expression.
M.I.T. and C.D. conceived the project and formulated the research plan; M.I.T, A.R. and C.D. supervised the experiments; M.L.G. provided technical assistance; K.S., M.M. set up the pipeline for the analyzes. M.I.T. and C.D. performed the data analyses; C.D. and E.M. helped with data analyzes and interpretations; M.I.T. and C.D. wrote the article with inputs from all the authors.
Footnotes
1 This work was supported by a grant overseen by the French National Research Agency (ANR) as part of the “Investments d’Avenir” Programme (LabEx BASC; ANR-11-LABX-0034) to C.D, as well as a grant from Institut de la Recherche Agronomique to A.R. (StaterFS2015-BAP-UMR320-FloSeq); M.M. was financed by GQE-Le Moulon and K.S. by Institut Diversité, Ecologie et Evolution du Vivant (FR3284 CNRS).