Aminooxyacetic acid (АОА), inhibitor of 1-aminocyclopropane-1-carboxilic acid (AСС) synthesis, suppresses self-incompatibility-induced programmed cell death in self-incompatible Petunia hybrida L. pollen tubes.

Self-incompatibility (SI) is genetically determined reproductive barrier preventing inbreeding and thereby providing the maintenance of plant species diversity. At present, active studies of molecular bases of SI mechanisms are underway. S-RNAse-based SI in Petunia hybrida L. is a self-/non-self recognition system that allows the pistil to reject self pollen and to accept non-self pollen for outcrossing. In the present work, using fluorescent methods including the TUNEL method allowed us to reveal the presence of markers of programmed cell death (PCD), such as DNA fragmentation, in growing in vivo petunia pollen tubes during the passage of the SI reaction. The results of statistical analysis reliably proved that PCD is the factor of S-RNAse-based SI. It was found that preliminary treatment before self-pollination of stigmas of petunia self-incompatible line with aminooxyacetic acid (AOA), inhibitor of ACC synthesis, led to stimulation of pollen tubes growth when the latter did not exhibit any hallmarks of PCD. These data argue in favor of assumption that ethylene controls the passage of PCD in incompatible pollen tubes in the course of S-RNAse-based SI functioning. The involvement of the hormonal regulation in SI mechanism in P. hybrida L. is the finding observed by us for the first time.

[Influence of genotype, explant type and component of culture medium on in vitro callus induction and shoot organogenesis of tomato (Solanum lycopersicum L.)].

The influence of explant type as well as of the type of growth regulators and concentration on callus induction processes and somatic organogenesis of shoots was studied in vitro on four tomato genotypes of Russian breeding. Cytological study of callus tissue was conducted. It was established that tomato varieties possess a substantially greater ability to indirect shoot organogenesis compared with the F1 hybrid. The highest frequency of somatic organogenesis of shoots, as well as their number per explant, was observed for most of the genotypes studied during the cultivation of cotyledons on Murashige-Skoog culture medium containing 2 mg/l of zeatin in combination with 0.1 mg/l of 3-indoleacetic acid. An effective protocol of indirect somatic organogenesis of shoots from different explants of tomato varieties with a frequency of more than 80% was developed.

[Abnormal floral meristem development in transgenic tomato plants do not depend on the expression of genes encoding defense-related PR-proteins and antimicrobial peptides].

In this study, the morphological and cytoembryological analyses of the tomato plants transformed with the genes encoding chitin-binding proteins (ac and RS-intron-Shir) from Amaranthus caudatus L. andA. retroflexus L., respectively, as well as the gene amp2 encoding hevein-like antimicrobial peptides from Stellaria media L., have been performed. The transgenic lines were adapted to soil and grown the greenhouse. The analysis of putative transgenic tomato plants revealed several lines that did not differ phenotypically from the wild type plants and three lines with disruption in differentiation of the inflorescence shoot and the flower, as well as the fruit formation (modified plants of each line were transformed with a single gene as noted before). Abnormalities in the development of the generative organs were maintained for at least six vegetative generations. These transgenic plants were shown to be defective in the mail gametophyte formation, fertilization, and, consequently, led to parthenocarpic fruits. The detailed analysis of growing ovules in the abnormal transgenic plants showed that the replacement tissue was formed and proliferated instead of unfertilized embryo sac. The structure of the replacement tissue differed from both embryonic and endosperm tissue of the normal ovule. The formation of the replacement tissue occurred due to continuing proliferation of the endothelial cells that lost their ability for differentiation. The final step in the development of the replacement tissue was its death, which resulted in the cell lysis. The expression of the genes used was confirmed by RT-PCR in all three lines with abnormal phenotype, as well as in several lines that did not phenotypically differ from the untransformed control. This suggests that abnormalities in the organs of the generative sphere in the transgenic plants do not depend on the expression of the foreign genes that were introduced in the tomato genome. Here, we argue that agrobacterial transformation affects, directly or indirectly, expression of genes encoding for transcription factors that can activate a gene cascade responsible for the normal plant development.