[What Does the WOX Say? Review of Regulators, Targets, Partners].

WOX (WUSCHEL-RELATED HOMEOBOX) is a family of homeodomain-containing transcription factors in plants. WOX proteins maintain the activity of different types of meristems and regulate the formation of plant organs, controlling cell proliferation and differentiation. Study of the WOX family is important for the development of plant transformation and genome editing techniques. Here we review the functions of the WOX transcription factors as well as their targets, partners, and regulators. The WOX family can be divided into three phylogenetically distinct clades; so-called ancient, intermediate, and WUS clade; each clade is covered in a separate section. The WOX genes of Arabidopsis thaliana are described most comprehensively, with their orthologs in other plant species also considered. Summary tables with the described targets, regulators and partners of WOX family members are provided.

Agrobacterial tumors interfere with nodulation and demonstrate the expression of nodulation-induced CLE genes in pea.

CLAVATA (CLV) system including CLV1-like kinase and CLE-peptides is the part of the AON (autoregulation of nodulation) that controls nodule number in legume plants. Moreover, CLV system plays a key role in meristems, where it regulates the expression of WOX genes in organizing centers. Recently, we found that WOX5 homolog in pea is also expressed in nodules and in tumors induced by Agrobacterium tumefaciens. Based on this, we hypothesized that both nodules and agrobacterial tumors may be regulated by and may trigger the same components of AON, including the same WOX and CLV genes. Here, we found that pea plants with agrobacterial tumors induced prior to rhizobial inoculation had reduced the number of nodules. This effect was absent in pea sym29 mutant defective in CLV1-like kinase, the key component of AON. That suggests that agrobacterial tumors may produce a signal activating CLV1-like kinase and thereby decrease the nodule number. Since CLE peptides are known to act upstream of CLV1-like kinase, expression analysis of CLE genes has been performed both in developing nodules and tumors. Overall, 45 CLE genes were identified, and among them nine nodulation-induced CLEs were found in pea. In agrobacterial tumors, no expression of nodule-specific CLE genes the homologues of which inhibit nodulation in other legumes was observed. However, increased expression of two other nodulation-induced CLE genes was observed in agrobacterial tumors, suggesting that CLE genes are expressed in tumors that may still contribute to autoregulatory processes suppressing nodulation.

[Transcription Factors in Developmental Genetics and the Evolution of Higher Plants].

Transcription factors play an essential role in controlling various developmental programs in plants, coordinating the action of any genetic network. Among the most important groups of plant transcription factors are the homeodomain-containing transcription factors, in particular, those belonging to the KNOX and WOX families, the functions of which are associated with regulation of the meristem activity, development of the aboveground and underground parts of plants, and control of embryogenesis. This review examines the role of KNOX and WOX transcription factors in various developmental programs, as well as in the evolutionary complication of the body plan in terrestrial plants.

[Expression of the WOX and PIN Genes in the Course of Somatic and Zygotic Embryogenesis of a Medicago truncatula].

Comparative analysis of the expression of the WOXand PINgenes in ovules and in the course of somatic embryogenesis of Medicago truncatula Gaertn was performed. It was shown that some WOX and PIN genes that had an increased expression level in ovules (MtWOX11-like, STENOFOLIA, MTR_2g015000, and MtPIN10) were also activated in the course of somatic embryogenesis. At the same time, the WOX and PIN genes, the expression level of which was low in ovules, did not show transcription activation associated with somatic embryogenesis. These data allow the assumption that the same regulatory mechanisms can be involved in the control of the early stages of somatic and zygotic embryogenesis.