Browsing by Author "Smart, Lawrence B."
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Item Evolution of a ZW sex chromosome system in willows(2023) Hu, Nan (TTU); Sanderson, Brian J.; Guo, Minghao (TTU); Feng, Guanqiao (TTU); Gambhir, Diksha (TTU); Hale, Haley; Wang, Deyan; Hyden, Brennan; Liu, Jianquan; Smart, Lawrence B.; DiFazio, Stephen P.; Ma, Tao; Olson, Matthew S. (TTU)Transitions in the heterogamety of sex chromosomes (e.g., XY to ZW or vice versa) fundamentally alter the genetic basis of sex determination, however the details of these changes have been studied in only a few cases. In an XY to ZW transition, the X is likely to give rise to the W because they both carry feminizing genes and the X is expected to harbour less genetic load than the Y. Here, using a new reference genome for Salix exigua, we trace the X, Y, Z, and W sex determination regions during the homologous transition from an XY system to a ZW system in willow (Salix). We show that both the W and the Z arose from the Y chromosome. We find that the new Z chromosome shares multiple homologous putative masculinizing factors with the ancestral Y, whereas the new W lost these masculinizing factors and gained feminizing factors. The origination of both the W and Z from the Y was permitted by an unexpectedly low genetic load on the Y and this indicates that the origins of sex chromosomes during homologous transitions may be more flexible than previously considered.Item A General Model to Explain Repeated Turnovers of Sex Determination in the Salicaceae(2021) Yang, Wenlu; Wang, Deyan; Li, Yiling; Zhang, Zhiyang; Tong, Shaofei; Li, Mengmeng; Zhang, Xu; Zhang, Lei; Ren, Liwen; Ma, Xinzhi; Zhou, Ran; Sanderson, Brian J.; Keefover-Ring, Ken; Yin, Tongming; Smart, Lawrence B.; Liu, Jianquan; DiFazio, Stephen P.; Olson, Matthew; Ma, TaoDioecy, the presence of separate sexes on distinct individuals, has evolved repeatedly in multiple plant lineages. However, the specific mechanisms by which sex systems evolve and their commonalities among plant species remain poorly understood. With both XY and ZW sex systems, the family Salicaceae provides a system to uncover the evolutionary forces driving sex chromosome turnovers. In this study, we performed a genome-wide association study to characterize sex determination in two Populus species, P. euphratica and P. alba. Our results reveal an XY system of sex determination on chromosome 14 of P. euphratica, and a ZW system on chromosome 19 of P. alba. We further assembled the corresponding sex-determination regions, and found that their sex chromosome turnovers may be driven by the repeated translocations of a Helitron-like transposon. During the translocation, this factor may have captured partial or intact sequences that are orthologous to a type-A cytokinin response regulator gene. Based on results from this and other recently published studies, we hypothesize that this gene may act as a master regulator of sex determination for the entire family. We propose a general model to explain how the XY and ZW sex systems in this family can be determined by the same RR gene. Our study provides new insights into the diversification of incipient sex chromosomes in flowering plants by showing how transposition and rearrangement of a single gene can control sex in both XY and ZW systems.Item Integrative genomics reveals paths to sex dimorphism in Salix purpurea L(2021) Hyden, Brennan; Carlson, Craig H.; Gouker, Fred E.; Schmutz, Jeremy; Barry, Kerrie; Lipzen, Anna; Sharma, Aditi; Sandor, Laura; Tuskan, Gerald A.; Feng, Guanqiao (TTU); Olson, Matthew S. (TTU); DiFazio, Stephen P.; Smart, Lawrence B.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.Item A willow sex chromosome reveals convergent evolution of complex palindromic repeats(2020) Zhou, Ran; Macaya-Sanz, David; Carlson, Craig H.; Schmutz, Jeremy; Jenkins, Jerry W.; Kudrna, David; Sharma, Aditi; Sandor, Laura; Shu, Shengqiang; Barry, Kerrie; Tuskan, Gerald A.; Ma, Tao; Liu, Jianquan; Olson, Matthew S.; Smart, Lawrence B.; DiFazio, Stephen P.Background: Sex chromosomes have arisen independently in a wide variety of species, yet they share common characteristics, including the presence of suppressed recombination surrounding sex determination loci. Mammalian sex chromosomes contain multiple palindromic repeats across the non-recombining region that show sequence conservation through gene conversion and contain genes that are crucial for sexual reproduction. In plants, it is not clear if palindromic repeats play a role in maintaining sequence conservation in the absence of homologous recombination. Results: Here we present the first evidence of large palindromic structures in a plant sex chromosome, based on a highly contiguous assembly of the W chromosome of the dioecious shrub Salix purpurea. The W chromosome has an expanded number of genes due to transpositions from autosomes. It also contains two consecutive palindromes that span a region of 200 kb, with conspicuous 20-kb stretches of highly conserved sequences among the four arms that show evidence of gene conversion. Four genes in the palindrome are homologous to genes in the sex determination regions of the closely related genus Populus, which is located on a different chromosome. These genes show distinct, floral-biased expression patterns compared to paralogous copies on autosomes. Conclusion: The presence of palindromes in sex chromosomes of mammals and plants highlights the intrinsic importance of these features in adaptive evolution in the absence of recombination. Convergent evolution is driving both the independent establishment of sex chromosomes as well as their fine-scale sequence structure.