Can nucleotide diversity patterns in Pinus pinaster lignification transcription factors be explained by demography or selection?

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Lepoittevin, Camille | Hubert, François | Plomion, Christophe | Garnier‐géré, Pauline

Edité par CCSD -

International audience. Lignification is an essential process in trees, playing a key role in sap conducting, mechanical support or biotic and abiotic stress resistance. Although structural genes coding for enzymes of the lignin biosynthetic pathway are well known, we are only beginning to understand the mechanisms that regulate this process. This study aimed at assessing the nucleotide diversity of 9 transcription factors which are thought to play key regulatory roles in conifer lignification, namely MYB1, 2, 4, 5, 8 and 14, HDZip31, LIM2 and SCL1. Individuals were sampled in Pinus pinaster natural populations from the French Atlantic coast. The “cisregulatory evolution” theory states that transcription factors possess little variation due to the large number of downstream target genes that would be affected, and are submitted to strong purifying selection. In line with this theory, nucleotide diversity observed in the 9 TFs was twice lower than for other structural genes from the lignin pathway. We then modelled a large range of bottleneck scenari and tested whether patterns of diversity at each gene departed from expectations. We will present the contrasting results across the different genes and discuss the consistency of the best fitting models with maritime pine species demographic history.

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