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1. Genome duplication effects on functional traits and fitness are genetic context and species dependent: studies of synthetic polyploid Fragaria

   https://doi.org/10.1002/ajb2.1377  

   Wei, Na ; Du, Zhaokui ; Liston, Aaron ; Ashman, Tia‐Lynn ( November 2019 , American Journal of Botany)

   Divergence in functional traits and adaptive responses to environmental change underlies the ecological advantage of polyploid plants in the wild. While established polyploids may benefit from combined outcomes of genome doubling, hybridization, and polyploidy‐enabled adaptive evolution, whether genome doubling alone can drive ecological divergence or whether the outcome is genetically variable remains less clear.

   Using synthetic, colchicine‐induced, autotetraploid (4x) plants derived from self‐pollinated diploid (2x) seeds, and their colchicine‐treated but unconverted diploid (2x.nc) full sibs from two diploid wild strawberry taxa (Fragaria vescasubsp.vescaandF. vescasubsp.bracteata), we examined the effects of genome doubling on functional traits, heat stress tolerance, and fitness components across taxa and maternal families (i.e., genetic families) within taxa.

   Comparisons between 2xand 2x.ncplants indicated a negligible effect of colchicine treatment on functional traits. Genome doubling increased stomatal length and decreased stomatal density, specific leaf area, and leaf vein density, recapitulating patterns observed in wild polyploidFragaria. Trichome density, heat stress tolerance, and relative growth rate were not significantly affected by genome doubling. Although clonal reproduction was reduced in response to genome doubling, this effect was strongly genetic‐family dependent.

   The results suggest that genome doubling during incipient speciation alone can generate ecological divergence and variation among genetic lineages. This response potentially allows for rapid short‐term evolutionary adaptation and fuels genomic diversity and independent origins of polyploidy.

    

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2. Mechanism of fertilization-induced auxin synthesis in the endosperm for seed and fruit development

   https://doi.org/10.1038/s41467-022-31656-y  

   Guo, Lei ; Luo, Xi ; Li, Muzi ; Joldersma, Dirk ; Plunkert, Madison ; Liu, Zhongchi ( July 2022 , Nature Communications)

   The dominance of flowering plants on earth is owed largely to the evolution of maternal tissues such as fruit and seedcoat that protect and disseminate the seeds. The mechanism of how fertilization triggers the development of these specialized maternal tissues is not well understood. A key event is the induction of auxin synthesis in the endosperm, and the mobile auxin subsequently stimulates seedcoat and fruit development. However, the regulatory mechanism of auxin synthesis in the endosperm remains unknown. Here, we show that a type I MADS box geneAGL62is required for the activation of auxin synthesis in the endosperm in bothFragaria vesca, a diploid strawberry, and in Arabidopsis. Several strawberryFveATHBgenes were identified as downstream targets ofFveAGL62and act to repress auxin biosynthesis. In this work, we identify a key mechanism for auxin induction to mediate fertilization success, a finding broadly relevant to flowering plants.

    

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3. DeepTetrad: high‐throughput image analysis of meiotic tetrads by deep learning in Arabidopsis thaliana

   https://doi.org/10.1111/tpj.14543  

   Lim, Eun‐Cheon ; Kim, Jaeil ; Park, Jihye ; Kim, Eun‐Jung ; Kim, Juhyun ; Park, Yeong Mi ; Cho, Hyun Seob ; Byun, Dohwan ; Henderson, Ian R. ; Copenhaver, Gregory P. ; et al ( October 2019 , The Plant Journal)

   Meiotic crossovers facilitate chromosome segregation and create new combinations of alleles in gametes. Crossover frequency varies along chromosomes and crossover interference limits the coincidence of closely spaced crossovers. Crossovers can be measured by observing the inheritance of linked transgenes expressing different colors of fluorescent protein inArabidopsispollen tetrads. Here we establish DeepTetrad, a deep learning‐based image recognition package for pollen tetrad analysis that enables high‐throughput measurements of crossover frequency and interference in individual plants. DeepTetrad will accelerate the genetic dissection of mechanisms that control meiotic recombination.

    

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4. RAD ‐seq linkage mapping and patterns of segregation distortion in sedges: meiosis as a driver of karyotypic evolution in organisms with holocentric chromosomes

   https://doi.org/10.1111/jeb.13267  

   Escudero, Marcial ; Hahn, Marlene ; Hipp, Andrew L. ( April 2018 , Journal of Evolutionary Biology)

   Meiotic drive, the class of meiotic mechanisms that drive unequal segregation of alleles among gametes, may be an important force in karyotype evolution. Its role in holocentric organisms, whose chromosomes lack localized centromeres, is poorly understood. We crossed two individuals of Carex scoparia(Cyperaceae) with different chromosome numbers (2n = 33^II = 66 × 2n = 32^II = 64) to obtain F1 individuals, which we then self‐pollinated to obtain second‐generation (F2) crosses. RAD‐seq was performed for 191 individuals (including the parents, five F1 individuals and 184 F2 individuals). Our F2 linkage map based on stringent editing of the RAD‐seq data set yielded 32 linkage groups. In the final map, 865 loci were located on a linkage map of 3966.99 cM (linkage groups ranged from 24.39 to 193.31 cM in length and contained 5–51 loci each). Three linkage groups exhibit more loci under segregation distortion than expected by chance; within linkage groups, loci exhibiting segregation distortion are clustered. This finding implicates meiotic drive in the segregation of chromosome variants, suggesting that selection of chromosome variants in meiosis may contribute to the establishment and fixation of chromosome variants inCarex, which is renowned for high chromosomal and species diversity. This is an important finding as previous studies demonstrate that chromosome divergence may play a key role in differentiation and speciation inCarex.

    

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5. Molecular bases of strawberry fruit quality traits: Advances, challenges, and opportunities

   https://doi.org/10.1093/plphys/kiad376  

   Liu, Zhongchi ; Liang, Tong ; Kang, Chunying ( July 2023 , Plant Physiology)

   The strawberry is one of the world's most popular fruits, providing humans with vitamins, fibers, and antioxidants. Cultivated strawberry (Fragaria × ananassa) is an allo-octoploid and highly heterozygous, making it a challenge for breeding, quantitative trait locus (QTL) mapping, and gene discovery. Some wild strawberry relatives, such as Fragaria vesca, have diploid genomes and are becoming laboratory models for the cultivated strawberry. Recent advances in genome sequencing and CRISPR-mediated genome editing have greatly improved the understanding of various aspects of strawberry growth and development in both cultivated and wild strawberries. This review focuses on fruit quality traits that are most relevant to the consumers, including fruit aroma, sweetness, color, firmness, and shape. Recently available phased-haplotype genomes, single nucleotide polymorphism (SNP) arrays, extensive fruit transcriptomes, and other big data have made it possible to locate key genomic regions or pinpoint specific genes that underlie volatile synthesis, anthocyanin accumulation for fruit color, and sweetness intensity or perception. These new advances will greatly facilitate marker-assisted breeding, the introgression of missing genes into modern varieties, and precise genome editing of selected genes and pathways. Strawberries are poised to benefit from these recent advances, providing consumers with fruit that is tastier, longer-lasting, healthier, and more beautiful.

    

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