In addition to classic phytohormones, such as auxin, cytokinin, ethylene, gibberellin, and abscisic acid, plant peptide hormones are also involved in various aspects of growth and...

Radish (Raphanus sativus L.) is a widespread agricultural plant forming storage root due to extensive secondary growth which involves cambium proliferation and differentiation of secondary conductive tissues. Closely related to the model object Arabidopsis thaliana, radish is a suitable model for studying processes of secondary growth and storage root development. CLE peptides are a group of peptide phytohormones which play important role in the regulation of primary meristems such as SAM, RAM, and procambium, as well as secondary meristems. However, the role of CLE peptides in lateral growth of root during storage root formation has not been studied to date. In present work we studied the role of CLE peptides in the development of storage root in radish. We have identified 18 CLE genes of radish (RsCLEs) and measured their expression in various plant organs and also at different stages of root development in R. sativus and Raphanus raphanistrum—its close relative which does not form storage root. We observed significant decline of expression levels for genes RsCLE1, 2, 11, 13, and 16, and also multifold increase of expression levels for genes RsCLE19, and 41 during secondary root growth in R. sativus but not in R. raphanistrum. Expression of RsCLE 2, 19, and 41 in R. sativus root was confined to certain types of tissues while RsCLE1, 11, 13, and 16 expressed throughout the root. Experiments on overexpression of RsCLE2, 19 and 41 or treatment of radish plants with synthetic CLE peptides revealed that CLE19 and CLE2 increase the number of xylem elements, and CLE41 induces the formation of extra cambium foci in secondary xylem. Expression levels of RsCLE2 and 19 strongly decrease in response to exogenous cytokinin, while auxin causes dramatic increase of RsCLE19 expression level and decrease of RsCLE41 expression. Our data allow us to hypothesize about the role of RsCLE2, 19 and 41 genes in the development of storage root of Raphanus sativus, e.g. RsCLE19 may play a role in auxin-dependent processes of xylem differentiation and RsCLE41 stimulates cambium activity.

Endophytic bacteria can be used to overcome the effect of salinity stress and promote plant growth and nutrient uptake. Bacillus safensis colonizes a wide range of habitats due to survival in extreme environments and unique physiological characteristics, such as a high tolerance for salt, heavy metals, and ultraviolet and gamma radiations. The aim of our study was to examine the salt resistance of the endophytic strain TS3 B. safensis and its ability to produce phytohormones and verify its effect on plant yield in field trials and the alleviation of salt stress in pot experiments. We demonstrate that the strain TS3 is capable of producing enzymes and phytohormones such as IAA, ABA and tZ. In pot experiments with radish and oat plants in salinization, the strain TS3 contributed to the partial removal of the negative effect of salinization. The compensatory effect of the strain TS3 on radish plants during salinization was 46.7%, and for oats, it was 108%. We suppose that such a pronounced effect on the plants grown and the salt stress is connected with its ability to produce phytohormones. Genome analysis of the strain TS3 showed the presence of the necessary genes for the synthesis of compounds responsible for the alleviation of the salt stress. Strain B. safensis TS3 can be considered a promising candidate for developing biofertilizer to alleviate salt stress and increase plant yield.

CLE genes encode a group of small secretory peptides, which regulate cell proliferation and differentiation in plants. CLE genes have been studied in many plants; however, little is known about this gene family in potato. In this study, we characterized members of the CLE gene family in potato Solanum tuberosum (StCLE) and comprehensively analyzed their phylogenetic relationships, structure, and expression patterns. Using available transcriptomic data, we found a relative high expression level of StCLE8, StCLE12, and StCLE13 in stolons and tubers. Real-time PCR analysis showed that the StCLE23 gene was upregulated by water deficiency, whereas the expression of StCLE4 and StCLE10 was induced by nitrogen supply. Besides that, using data from transcriptomic studies obtained previously for plants with the induction the StBEL5 gene, a positive regulator of tuber development, we found that StCLE4 was among genes upregulated in response to StBEL5 induction, suggesting that StCLE4 could be a target of StBEL5 transcription factor. However, we did not reveal a direct binding of StBEL5 to the regulatory sequences of StCLE4 using yeast one-hybrid assay. Taken together, our data provide basic information for future functional studies of CLE peptides in potato growth and tuberization and in response to various environmental stimuli.

Lateral meristems (pericycle, procambium and cambium, phellogen) are positioned in parallel to the lateral surface of the organ, where they are present, and produce concentric layers of...