| 1. |
- Gutiérrez-Valencia, Juanita, 1991-, et al.
(författare)
-
Genetic Causes and Genomic Consequences of Breakdown of Distyly in Linum trigynum
- 2024
-
Ingår i: Molecular biology and evolution. - 0737-4038 .- 1537-1719. ; 41:5
-
Tidskriftsartikel (refereegranskat)abstract
- Distyly is an iconic floral polymorphism governed by a supergene, which promotes efficient pollen transfer and outcrossing through reciprocal differences in the position of sexual organs in flowers, often coupled with heteromorphic self-incompatibility. Distyly has evolved convergently in multiple flowering plant lineages, but has also broken down repeatedly, often resulting in homostylous, self-compatible populations with elevated rates of self-fertilization. Here, we aimed to study the genetic causes and genomic consequences of the shift to homostyly in Linum trigynum, which is closely related to distylous Linum tenue. Building on a high-quality genome assembly, we show that L. trigynum harbors a genomic region homologous to the dominant haplotype of the distyly supergene conferring long stamens and short styles in L. tenue, suggesting that loss of distyly first occurred in a short-styled individual. In contrast to homostylous Primula and Fagopyrum, L. trigynum harbors no fixed loss-of-function mutations in coding sequences of S-linked distyly candidate genes. Instead, floral gene expression analyses and controlled crosses suggest that mutations downregulating the S-linked LtWDR-44 candidate gene for male self-incompatibility and/or anther height could underlie homostyly and self-compatibility in L. trigynum. Population genomic analyses of 224 whole-genome sequences further demonstrate that L. trigynum is highly self-fertilizing, exhibits significantly lower genetic diversity genome-wide, and is experiencing relaxed purifying selection and less frequent positive selection on nonsynonymous mutations relative to L. tenue. Our analyses shed light on the loss of distyly in L. trigynum, and advance our understanding of a common evolutionary transition in flowering plants.
|
|
| 2. |
- Gutiérrez-Valencia, Juanita, et al.
(författare)
-
Genomic analyses of the Linum distyly supergene reveal convergent evolution at the molecular level
- 2022
-
Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 32:20, s. 4360-4371, 4371.e1-4371.e6
-
Tidskriftsartikel (refereegranskat)abstract
- Supergenes govern multi-trait-balanced polymorphisms in a wide range of systems; however, our understanding of their origins and evolution remains incomplete. The reciprocal placement of stigmas and anthers in pin and thrum floral morphs of distylous species constitutes an iconic example of a balanced polymorphism governed by a supergene, the distyly S-locus. Recent studies have shown that the Primula and Turnera distyly supergenes are both hemizygous in thrums, but it remains unknown whether hemizygosity is pervasive among distyly S-loci. As hemizygosity has major consequences for supergene evolution and loss, clarifying whether this genetic architecture is shared among distylous species is critical. Here, we have characterized the genetic architecture and evolution of the distyly supergene in Linum by generating a chromosome-level genome assembly of Linum tenue, followed by the identification of the S-locus using population genomic data. We show that hemizygosity and thrum-specific expression of S-linked genes, including a pistil-expressed candidate gene for style length, are major features of the Linum S-locus. Structural variation is likely instrumental for recombination suppression, and although the non-recombining dominant haplotype has accumulated transposable elements, S-linked genes are not under relaxed purifying selection. Our findings reveal remarkable convergence in the genetic architecture and evolution of independently derived distyly supergenes, provide a counterexample to classic inversion-based supergenes, and shed new light on the origin and maintenance of an iconic floral polymorphism.
|
|
| 3. |
- Losvik, Aleksandra, 1985-
(författare)
-
Barley defense genes against aphids
- 2018
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aphids are insect pests with major importance worldwide. By feeding from plant phloem, they directly withdraw nutrients. The feeding injury is often visible in the form of leaf rolling, chlorosis, necrosis or plant deformation. Their pest status is attributed also to vectoring of plant viruses. Aphid infestation on crop plants is currently managed with the use of pesticides, which may pose a threat to the environment. An alternative approach would be to identify and characterize genetic factors contributing to aphid resistance, as well as agents inducing resistance, with the intention to use this knowledge in breeding programs.The aim of this thesis was to identify such resistance genes and characterize their involvement in plant-aphid interactions. This was accomplished using two approaches. Firstly, two putative aphid-resistance genes from barley, CI2c encoding a chymotrypsin inhibitor and LOX2.2 encoding a lipoxygenase, were transformed into Arabidopsis and/or barley and the effects of transformation were studied with regard to the performance of two aphid species. One was the specialist bird cherry-oat aphid (Rhopalosiphum padi L.), which is a pest on major cereals, and the other was a generalist, the green peach aphid (Myzus persicae Sulzer), which is a pest on plants belonging to more than 40 families. The effects of transformation were also studied concerning effects on the expression of other defense-related genes in the transgenic plants. Secondly, the effects of plant treatment with volatiles were studied with regard to induction of plant resistance, followed by tests with bird cherry-oat aphid on the treated plants.The study of overexpression of CI2c showed that the gene product transiently reduced green peach aphid fecundity on transgenic Arabidopsis, but indirectly decreased this aphid’s avoidance of barley by suppressing defense. The transformation had no effects on bird cherry-oat aphids’ behaviour or fecundity. Overexpression of LOX2.2 was shown to affect expression of other genes regulated by jasmonic acid and decreased the short-term fecundity of both the bird cherry-oat aphid and the green peach aphid on barley. The study of volatile treatments supported the idea that resistance against aphids can be induced by application of volatiles. Several defense gene sequences were induced by application of methyl salicylate, methyl jasmonate and (Z)-3-hexen-1-ol. Of the three volatiles tested, methyl jasmonate showed the greatest potential as inducing agent, causing a short-term reduction in aphid fecundity.To conclude, this thesis supports the ideas that the barley genes CI2c and LOX2.2 play a role in resistance against aphids and that moderate aphid resistance can be induced by external factors. Aphids may be directly affected by the gene product or there may be an indirect effect, caused by changes in the expression of other genes involved in plant defense. The observed negative effects on aphids were of moderate magnitude and it is proposed that acting individually, those genes are not likely to cause a strong negative effect, but they may contribute to provide resistance to aphids.
|
|
| 4. |
- Losvik, Aleksandra, 1985-, et al.
(författare)
-
Effects of treatments of barley with methyl salicylate, methyl jasmonate or (Z)-3-hexen-1-ol on barley gene expression and fecundity of bird cherry-oat aphid
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Aphids are serious pests on crop plants. Chemical control is currently the most efficient and widely used method to control aphid populations; however it has negative environmental consequences. Inducing aphid resistance in plants by volatile treatments may be an alternative, less harmful measure. Here, we have studied volatile induced responses in barley (Hordeum vulgare L.) and their effect on bird cherry-oat aphid (Rhopalosiphum padi L.). Barley cultivars Scandium, Lina and Barke were exposed to methyl salicylate, methyl jasmonate or (Z)-3-hexen-1-ol, plant volatiles which all have been shown to induce arthropod resistance. Treated plants were analyzed for changes in gene expression using RT-qPCR method, with focus on genes related to plant defense. Genes encoding a calcium-binding EF-hand protein, a protease inhibitor and lipoxygenase 2.2 were induced by exposure to methyl salicylate. Methyl jasmonate and (Z)-3-hexen-1-ol treatments were found to up-regulate an allene oxide synthase gene and lipoxygenase 2.1. Methyl salicylate treatment prolonged the pre-reproductive period and reduced the intrinsic rate of aphid population increase on cultivar Scandium, but had no effect on fecundity. Treatments with methyl jasmonate reduced aphid fecundity over a seven day period on two out of three tested cultivars. We did not observe any effects of methyl salicylate or methyl jasmonate treatments on aphid life span or total offspring during the life. In conclusion, we have demonstrated that all tested volatiles induce putative defense related genes, but only methyl jasmonate showed potential for protecting barley against aphids.
|
|
