Integrative genomics reveals paths to sex dimorphism in Salix purpurea L.

Authors: HYDEN, BRENNAN - Cornell University; CARLSON, CRAIG - Cornell University; Gouker, Fred; SCHMUTZ, JEREMY - Department Of Energy Joint Genome; BARRY, KERRIE - Department Of Energy Joint Genome; LIPZEN, ANNA - Department Of Energy Joint Genome; SHARMA, ADITI - Department Of Energy Joint Genome; SANDOR, LAURA - Department Of Energy Joint Genome; TUSKAN, GERALD - Oak Ridge National Laboratory; FENG, GUANGIO - Texas Tech University; OLSON, MATTHEW - Texas Tech University; DIFAZIO, STEPHEN - West Virginia University; SMART, LAWRENCE - Cornell University

Submitted to: Horticulture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2021
Publication Date: 8/1/2021
Citation: Hyden, B., Carlson, C.H., Gouker, F.E., Schmutz, J., Barry, K., Lipzen, A., Sharma, A., Sandor, L., Tuskan, G.A., Feng, G., Olson, M.S., Difazio, S.P., Smart, L.B. 2021. Integrative genomics reveals paths to sex dimorphism in Salix purpurea L. . Horticulture Research. https://doi.org/10.1038/s41438-021-00606-y.
DOI: https://doi.org/10.1038/s41438-021-00606-y

Interpretive Summary: Individual willow and poplar plants are either male or female, which is determined by the inheritance of genes on a sex chromosome. Purple osier willow (Salix purpurea), is widely cultivated across the Northeast and Midwest United States along with Eastern and Central Canada for bioenergy, biomass, bioproducts, and conservation purposes. Willow is of particular interest for use in understanding plant sex determination since it has been found to be associated with biomass and growth traits, including yield indicators such as stem diameter and leaf size, as well as influencing pollinator and pest attraction. Understanding sex determination will therefore enable more effective breeding strategies. With a relatively short life cycle and a fully assembled reference genome, willow is uniquely poised to answer scientific questions relating to sex-determination in woody plants. While willow and poplar are closely related, our results using whole genome sequencing approaches in purple osier willow indicates that the genetic mechanism controlling sex in willow is different from that in poplar which we have shown through the identification of eleven genes regulating sex determination.

Technical Abstract: Sex dimorphism and gene expression were studied in developing catkins in 159 F2 individuals from the bioenergy crop Salix purpurea, and potential mechanisms and pathways for regulating sex development were explored. Differential expression, eQTL, bisulfite sequencing, and network analysis were used to characterize sex dimorphism, detect candidate master regulator genes, and identify pathways through which the sex determination region (SDR) may mediate sex dimorphism. Eleven genes are presented as candidates for master regulators of sex, supported by gene expression and network analyses. These include genes putatively involved in hormone signaling, epigenetic modification, and regulation of transcription. eQTL analysis revealed a suite of transcription factors and genes involved in secondary metabolism and floral development that were predicted to be under direct control of the sex determination region. Furthermore, data from bisulfite sequencing and small RNA sequencing revealed strong differences in expression between males and females that would implicate both of these processes in sex dimorphism pathways. These data indicate that the mechanism of sex determination in Salix purpurea is likely different from that observed in the related genus Populus. This further demonstrates the dynamic nature of SDRs in plants, which involves a multitude of mechanisms of sex determination and a high rate of turnover.