Expression of Recombinant SPO11 Genes Locally Alters Crossing Over in Tomato
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T GENETICS
Expression of Recombinant SPO11 Genes Locally Alters Crossing Over in Tomato V. V. Komakhinaa, A. A. Krinitsinaa, b, N. A. Milyukovaa, and R. A. Komakhina, * a
All-Russia Research Institute of Agricultural Biotechnology, Moscow, 127550 Russia b Moscow State University, Moscow, 119234 Russia *e-mail: [email protected] Received October 14, 2019; revised November 26, 2019; accepted December 5, 2019
Abstract—Nonrandom distribution of meiotic recombination events along the chromosomes shapes the diversity of potential genetic combinations among the offspring. To redistribute the chromosomal regions involved in recombination events, it was proposed to use meiosis-specific genes of Spo11 proteins (generating double-strand DNA breaks) from phylogenetically different organisms. For these purposes, transgenic tomato plants expressing native SPO11 genes from yeast (Saccharomyces cerevisae) or Arabidopsis thaliana under the control of constitutive 35S CaMV promoter were constructed. Genetic analysis showed that expression of both target SPO11 genes partly disturbed the monogenic inheritance of marker Wv:wv alleles in chromosome 2 and suppressed the crossing over in the region between the wv and d genes. A stable negative correlation between the target gene expression levels and the decrease in the frequency of crossing over in the analyzed chromosomal region was found. The possible genetic mechanisms underlying the redistribution of crossovers along chromosome 2 resulting from the target SPO11 gene expression are discussed. Keywords: tomato, Solanum, hybrids, transgenic plants, SPO11 genes, recombination, crossing over, doublestrand breaks (DSBs) DOI: 10.1134/S1022795420090124
INTRODUCTION Meiotic recombination plays an important role in the evolution of eukaryotic organisms and is the major source of genetic variation in combinative plant breeding. The genetic variation that arose in heterozygotes in the course of meiosis is the combined result of the interaction of several fundamental mechanisms. One of these mechanisms is well known and is realized in the form of independent recombination of homologous chromosomes during the formation of haploid gametes. Two other mechanisms are based on the redistribution of single- and double-stranded DNA regions between homologs and are initiated in prophase of meiosis by programmed double-strand DNA breaks (DSBs), which throughout the genome are created by meiosis-specific DNA topoisomerases VI, consisting of the TopoVIA subunit, known as Spo11 [1], and TopoVIB subunit [2, 3]. The DSB repair pathways separate after the formation of the D-loop and lead to different recombination products [1]. The double-strand break repair path leads to crossing over, which is essential for the formation of chiasmata between homologs and their proper segregation in anaphase I [4]. Not all cases of DSB repair end with crossing over; for example, in Arabidopsis thaliana, about 200–300 DSBs per cell arise,
but only about 10 crossovers are observed in meiosis [5]. To maintain the genome i
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