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The St. P, and Y genomes are three important genomes in the tribe Triticeae, which includes many perennial species. To study polymorphisms within the chromosomes of the St, P, and Y genomes, a G1SH-F1SH method was developed that allowed them to be clearly distinguished. The karyotypes of five individuals from population Z1925 of Kengyilia grandiglumis (Keng) J.L. Yang et al. (2n = 6x = 42, StStPPYY) were analyzed. The results showed thai there were structural polymorphisms in all of the chromosomes from the three individual genomes. The polymorphisms were found mainly in the terminal regions of chromosomes and infrequently near the centromeric region. Of all the chromosomes, 1P, 1St, 1Y, 2Y, 3St, and 3Y showed the most polymorphisms. The polymorphisms within the individual chromosomes suggested that more extensive and scientific conclusions regarding the origin and evolution of genomes in wild species of Triticeae would be achieved by studying a population as a sampling and analysis unit. Key words: Triticeae, StPY genomes. G1SH-FISH, chromosomal structure, polymorphism. Les genomes St, P et Y sont presents chez plusieurs membres importants de la tribu des triticees, laquelle comprend plusieurs especes perennes. Afin d'etudier le polymorphisme au sein des chromosomes des genomes St, P et Y, une methode combinant des analyses GISH el FISH et permettanl de distinguer clairement ces chromosomes a ete mise au point. Les caryoiypes de cinq individus de la population Z1925 du Kengyilia gmndiglumis (Keng) J.L. Yang el al. (2n = 6x = 42, StStPPYY) ont ete analyses. Les resultants montrent qu'il y a du polymorphisme struciurel chez, tous les chromosomes de ces trois genomes. Les polymorphismes ont ete observes principalement au sein des regions terminales et, plus rarement, pres des regions centromeriques. De tons les chromosomes, 1P, 1St, 1Y, 2Y, 3St et 3Y etalent les plus polymorphes. Les polymorphismes au sein des chromosomes individuels suggerent que. pour arriver a des conclusions plus larges et mieux fondees scientifiquement sur l'origine et revolution des genomes au sein des especes sauvages de la tribu des triticees, il faudrait etudier une population en tant qu'unite d'echantillonnage et d'analyse. Mots-cles : triticees, genomes StPY, GISH-FISH, structure chromosomique, polymorphisme. [Traduit par la Redaction], Introduction There are 23 basic genomes in the tribe Triticeae (Dewey 1984: Love 1984), and the St, P, and Y genomes are important genomes of this group. The six perennial [...]

C4 photosynthesis increases the efficiency of carbon fixation by spatially separating high concentrations of molecular oxygen from Rubisco. The specialized leaf anatomy required for this separation evolved independently many times. The morphology of C4 root systems is also distinctive and adapted to support high rates of photosynthesis; however, little is known about the molecular mechanisms that have driven the evolution of C4 root system architecture. Using a mutant screen in the C4 model plant Setaria italica , we identify Siaux1-1 and Siaux1-2 as root system architecture mutants. Unlike in S. viridis , AUX1 promotes lateral root development in S. italica. A cell by cell analysis of the Siaux1-1 root apical meristem revealed changes in the distribution of cell volumes in all cell layers and a dependence of the frequency of protophloem and protoxylem strands on SiAUX1. We explore the molecular basis of the role of SiAUX1 in seedling development using an RNAseq analysis of wild-type and Siaux1-1 plants and present novel targets for SiAUX1 -dependent gene regulation. Using a selection sweep and haplotype analysis of SiAUX1 , we show that Hap-2412TT in the promoter region of SiAUX1 is an allele which is associated with lateral root number and has been strongly selected for during Setaria domestication. [ABSTRACT FROM AUTHOR]

C4 photosynthesis increases the efficiency of carbon fixation by spatially separating high concentrations of molecular oxygen from Rubisco. The specialized leaf anatomy required for this separation evolved independently many times. The morphology of C4 root systems is also distinctive and adapted to support high rates of photosynthesis; however, little is known about the molecular mechanisms that have driven the evolution of C4 root system architecture. Using a mutant screen in the C4 model plant Setaria italica, we identify Siaux1-1 and Siaux1-2 as root system architecture mutants. Unlike in S. viridis, AUX1 promotes lateral root development in S. italica. A cell by cell analysis of the Siaux1-1 root apical meristem revealed changes in the distribution of cell volumes in all cell layers and a dependence of the frequency of protophloem and protoxylem strands on SiAUX1. We explore the molecular basis of the role of SiAUX1 in seedling development using an RNAseq analysis of wild-type and Siaux1-1 plants and present novel targets for SiAUX1-dependent gene regulation. Using a selection sweep and haplotype analysis of SiAUX1, we show that Hap-2412TT in the promoter region of SiAUX1 is an allele which is associated with lateral root number and has been strongly selected for during Setaria domestication., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)