MutS‐Homolog2 silencing generates tetraploid meiocytes in tomato (Solanum lycopersicum)

Effective RNAi-Mediated Silencing of the Mismatch Repair MSH2 Gene Induces Sterility of Tomato Plants but Not an Increase in Meiotic Recombination

“…Note that we initially cultivated tomato transgenic plants with simultaneous silencing of the MSH2 gene and overexpression of SPO11 genes under "long-day" conditions. This is comparable to the results of a previously published study involving Arka Vikas MSH2-RNAi tomato lines, of which only one line with high silencing efficiency showed about 10% pollen viability, while the rest of the lines with lower silencing efficiency had a significantly higher pollen viability level [35]. However, our further results demonstrated that in MSH2-RNAi tomato plants, an acceptable level of the pollen viability is not always combined with the formation of fruits and seed sets.…”

“…However, the authors of that article reported that 20% of the transformants had ploidy disorders as a result of Agrobacterium transformation, and they were not used in further research. Later, in the Arka Vikas tomato cultivar, in response to the RNAi silencing of MSH2 with an efficiency of more than 80%, defects in the development of flowers and anthers, a low pollen viability level, tetraploid microsporocytes, low fruit productivity, and a reduced seed set were found [35]. However, in this research only one transgenic line of the three studied clearly demonstrated the phenotype described above.…”

“…In our study, we found, for the first time, that the expression of the MSH2 gene in the leaves of tomato plants was significantly lower when the duration of illumination was increased (Figures 4 and 7). Previously published studies do not mention the effect of the duration of illumination on the level of the MSH2 gene transcript in tomato plants [5,35]. Our observation itself may explain the greater efficiency of MSH2 gene transcript silencing by RNAi in MSH2-RNAi tomato plants under "long-day" conditions.…”

“…In our study, the MSH2-RNAi tomato plants with at least 97% silencing of the MSH2 transcript by RNAi under "long-day" conditions, did not form seed sets after self-pollination, despite an acceptable level of pollen viability. It was previously shown that, in the Arka Vikas MSH2-RNAi tomato line with silencing (>80%) of MSH2 by RNAi, low pollen viability (10%) was associated with the formation of 5-10% seeds [35]. In contrast, in the Arabidopsis MSH2 mutant lines the seed set on average was reduced to only 50% [33].…”

“…The exact molecular mechanisms leading to the loss of fertility are not clear. Only in the research on the Arka Vikas tomato cultivar with the RNAi silencing of MSH2, did the authors attempt to interrelate the decrease of pollen viability and plant fertility with the disruptions in meiosis leading to the reduction of the seed set [35].…”