Characterization of Phytohormones and Transcriptomic Profiling of the Female and Male Inflorescence Development in Manchurian Walnut (Juglans mandshurica Maxim.)
Abstract:Flowers are imperative reproductive organs and play a key role in the propagation of offspring, along with the generation of several metabolic products in flowering plants. In Juglans mandshurica, the number and development of flowers directly affect the fruit yield and subsequently its commercial value. However, owing to the lack of genetic information, there are few studies on the reproductive biology of Juglans mandshurica, and the molecular regulatory mechanisms underlying the development of female and mal… Show more
“…While leafing date was not a significant predictor, we note that the slope estimate is in the expected direction. Notably, the earliest leafing protogynous varieties have catkin buds roughly of similar size to the latest leafing protandrous varieties. Figure S10: Reanalysis of RNA-seq experiment from Li et al . (2022b).…”
Section: Supplementary Materialsmentioning
confidence: 99%
“…TPP genes were recently identified as differentially expressed across the transition to flowering in both J. sigillata and J. mandshurica (Lu et al . 2020; Li et al . 2022b).…”
Section: Introductionmentioning
confidence: 99%
“…Given the conserved non-coding G haplotype indels, and the lack of Juglans -wide trans-specific coding polymorphism in TPPD-1 , we hypothesized that the developmental differential between dichogamy types may be due to differential regulation of TPPD-1 during early floral development. We reanalyzed RNAseq data collected from male and female flower buds of J. mandshurica , where a TPP gene was one of a number of differentially expressed genes over the course of flowering (Li et al . 2022b).…”
Section: Introductionmentioning
confidence: 99%
“…Across two separate J. mandshurica datasets (Qin et al . 2021; Li et al . 2022b), the TPPD-1 ortholog shows increased expression in male buds from samples with protogynous genotypes (Figs.…”
The maintenance of stable mating type polymorphisms is a classic example of balancing selection, underlying the nearly ubiquitous 50/50 sex ratio in species with separate sexes. One lesser known but intriguing example of a balanced mating polymorphism in angiosperms is heterodichogamy - polymorphism for opposing directions of dichogamy (temporal separation of male and female function in hermaphrodites) within a flowering season. This mating system is common throughout Juglandaceae, the family that includes globally important and iconic nut and timber crops - walnuts (Juglans), as well as pecan and other hickories (Carya). We show that two distinct genetic systems control heterodichogamous mating systems in these genera. In each genus, we find ancient (>50Mya) structural variants that segregate as trans-species polymorphisms. TheJuglanslocus maps to a ca. 20kb structural variant adjacent to gene with likely function in the trehalose-6-phosphate signaling pathway, which is known to regulate flowering time in Arabidopsis and inflorescence architecture in maize. Notably, an insertion in the dominant (protogynous) haplotype contains 8-12 complex tandem duplicates of the 3’ UTR of the gene, and transpecies polymorphism within the gene is restricted to the 3’ UTR. In contrast, theCaryaheterodichogamy locus maps to a ca. 200-450 kb cluster of tightly linked polymorphisms across 20 genes, some of which have known roles in flowering and are differentially expressed between morphs in floral primordia. The dominant (protogynous) haplotype in pecan, which is nearly always heterozygous and appears to rarely recombine, shows reduced genetic diversity and is over twice as long as its recessive counterpart due to proliferation of multiple transposable element families. We did not detect either genetic system in another heterodichogamous genus within the Juglandaceae, suggesting that additional genetic systems for heterodichogamy may yet remain undiscovered.
“…While leafing date was not a significant predictor, we note that the slope estimate is in the expected direction. Notably, the earliest leafing protogynous varieties have catkin buds roughly of similar size to the latest leafing protandrous varieties. Figure S10: Reanalysis of RNA-seq experiment from Li et al . (2022b).…”
Section: Supplementary Materialsmentioning
confidence: 99%
“…TPP genes were recently identified as differentially expressed across the transition to flowering in both J. sigillata and J. mandshurica (Lu et al . 2020; Li et al . 2022b).…”
Section: Introductionmentioning
confidence: 99%
“…Given the conserved non-coding G haplotype indels, and the lack of Juglans -wide trans-specific coding polymorphism in TPPD-1 , we hypothesized that the developmental differential between dichogamy types may be due to differential regulation of TPPD-1 during early floral development. We reanalyzed RNAseq data collected from male and female flower buds of J. mandshurica , where a TPP gene was one of a number of differentially expressed genes over the course of flowering (Li et al . 2022b).…”
Section: Introductionmentioning
confidence: 99%
“…Across two separate J. mandshurica datasets (Qin et al . 2021; Li et al . 2022b), the TPPD-1 ortholog shows increased expression in male buds from samples with protogynous genotypes (Figs.…”
The maintenance of stable mating type polymorphisms is a classic example of balancing selection, underlying the nearly ubiquitous 50/50 sex ratio in species with separate sexes. One lesser known but intriguing example of a balanced mating polymorphism in angiosperms is heterodichogamy - polymorphism for opposing directions of dichogamy (temporal separation of male and female function in hermaphrodites) within a flowering season. This mating system is common throughout Juglandaceae, the family that includes globally important and iconic nut and timber crops - walnuts (Juglans), as well as pecan and other hickories (Carya). We show that two distinct genetic systems control heterodichogamous mating systems in these genera. In each genus, we find ancient (>50Mya) structural variants that segregate as trans-species polymorphisms. TheJuglanslocus maps to a ca. 20kb structural variant adjacent to gene with likely function in the trehalose-6-phosphate signaling pathway, which is known to regulate flowering time in Arabidopsis and inflorescence architecture in maize. Notably, an insertion in the dominant (protogynous) haplotype contains 8-12 complex tandem duplicates of the 3’ UTR of the gene, and transpecies polymorphism within the gene is restricted to the 3’ UTR. In contrast, theCaryaheterodichogamy locus maps to a ca. 200-450 kb cluster of tightly linked polymorphisms across 20 genes, some of which have known roles in flowering and are differentially expressed between morphs in floral primordia. The dominant (protogynous) haplotype in pecan, which is nearly always heterozygous and appears to rarely recombine, shows reduced genetic diversity and is over twice as long as its recessive counterpart due to proliferation of multiple transposable element families. We did not detect either genetic system in another heterodichogamous genus within the Juglandaceae, suggesting that additional genetic systems for heterodichogamy may yet remain undiscovered.
“…Therefore, it is feasible to mine sex determination genes in S. chinensis using RNA-sequencing. It has also been shown that transcription factors, such as WRKY, MYB, and bHLH may play crucial roles in plant sex determination [ 17 , 18 , 19 ].…”
S. chinensis is a typical monoecious plant, and the number and development of female flowers determines the yield of S. chinensis. Due to a lack of genetic information, the molecular mechanism of sex differentiation in S. chinensis remains unclear. In this study, the combination of scanning electron microscopy (SEM) and RNA sequencing (RNA-seq) was used to understand the way of sex differentiation of S. chinensis and to mine the related genes of sex determination. The result shows the development of male and female S. chinensis flowers was completed at the same time, the unisexual S. chinensis flowers did not undergo a transition stage between sexes, and sex may have been determined at an early stage in flower development. The results of the gene function analysis of the plant hormone signaling pathway and sucrose metabolism pathway suggest that auxin and JA could be the key hormones for sex differentiation in S. chinensis, and sucrose may promote pollen maturation at the later stage of male flower development. Two AGAMOUS (GAG) genes, 10 AGAMOUS-like MADS-box (AGLs) genes, and the MYB, NAC, WRKY, bHLH, and Trihelix transcription factor families may play important roles in sex determination in S. chinensis. Taken together, the present findings provide valuable genetic information on flower development and sex determination in S. chinensis.
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