Sorghum is a crop plant that is grown for seeds, sucrose, forage and biofuel production. In all these applications, lignin is a superfluous component that decreases the efficiency of technological processes. Caffeoyl-coenzyme A O-methyltransferase (CCoAOMT) is an enzyme involved in monolignol synthesis that affects the efficiency of lignification and lignin composition. The sorghum genome harbors one CCoAOMT gene and six closely related CCoAOMT-like genes. The structures of four sorghum CCoAOMT-like enzymes suggest that these proteins might methylate caffeoyl coenzyme A and contribute to monolignol synthesis. In this study, two sorghum genes, CCoAOMT and one CCoAOMT-like, were found to be highly expressed in leaves, stems and immature seeds. The promoters of these genes possess clusters of transcription factor-binding sites specific for lignification, and this suggests that they are important for lignification. Phylogenetic analysis revealed that one sorghum CCoAOMT-like enzyme is closely related to ancestral cyanobacterial CCoAOMT-like proteins. The remaining CCoAOMT-like enzymes, including the one highly expressed in the leaves and stem, are closely related to CCoAOMT. Genes from these two groups possess different, evolutionarily conserved gene structures. The structure of the sorghum CCoAOMT-like protein from the ancestral clade was modeled and differences between enzymes from the two clades were analyzed. These results facilitate a better understanding of the evolution of genes involved in lignification, and provide valuable data for sorghum improvement through traditional breeding or molecular genetic techniques. The findings suggest that CCoAOMT-like genes might be recruited in lignification and raise questions of the frequency of such functional shifts.Electronic supplementary materialThe online version of this article (10.1007/s00438-018-1441-6) contains supplementary material, which is available to authorized users.

PR-10 proteins (pathogensis-related), ubiquitous within the plant kingdom, are usually encoded by multigene families. To date we have identified 10 homologous pr-10 genes in a yellow lupine cDNA library. Here, the structure and expression of two newly identified yellow lupine pr-10 genes (LlYpr10-2b and LlYpr10-2f) are presented. Many potential regulatory sites were found in both gene promoters including common ones as well as those unique for each gene. However, promoter deletion analysis in transgenic tobacco plants revealed similar patterns of reporter gene (gus) expression. Shortened fragments of both gene promoters studied caused high GUS activity in leaves (along vascular bundles), stamen stigma, anthers and pollen grains. When conjugated with longer LlYpr-10.2 promoter fragments, GUS was additionally present in petal edges. Only a long fragment of the LlYpr10-2b gene promoter caused GUS expression in the stem. In yellow lupine the pr-10.2 genes are present in all studied organs, but their level of expression depends on the stage of development and is affected by wounding, oxidative stress and salicylic acid treatment. Silencing of the Llpr-10.2b gene in 4-week-old yellow lupine plants did not lead to any visible symptoms, which suggests that the function of the silenced gene is supplemented by its close homologues, still present in the studied plants.

A gene for the D 9 desaturase specific to stearoyl-ACP (acyl carrier protein) was identified from yellow lupine (Lupinus luteus) cDNA and genomic libraries through the differential display method. The desaturase transcript appears in plants infected with Bradyrhizobium sp. (Lupinus) as revealed by Northern hybridization, RT-PCR and expression of b-glucuronidase under the desaturase promoter. A small amount of desaturase transcript was also detected in uninfected plants, which suggests that the gene does not belong to the strict nodule-specific sequences. The desaturase provides unsaturated fatty acids for additional cell membrane synthesis. During nodule and symbiosome development a peribacteroid membrane is formed and the requirement for membrane surface increases, thus the level of desaturase expression is also higher. Transgenic plants of Nicotiana tabacum with overexpression of the full-length lupine stearoyl-ACP desaturase sequence were obtained. They revealed higher content of unsaturated fatty acids (especially oleic acid) in comparison with control plants.

Phytohormones (plant hormones) play a role in the regulation of cellular activities including cell division, elongation and differentiation, pattern formation, organogenesis, reproduction, sex determination, and responses to abiotic and biotic stress. The phytohormonal signal transduction pathways operate via cytokinin perception by transmembrane receptors consisting of two domains: an extracellular domain responsible for hormone binding and an intracellular domain, sensory His / Asp kinase (HK). Upon phytohormone binding, the receptor undergoes a conformational change which activates its protein kinase activity. The phosphorylated intracellular domain transfers the phosphoryl group to the His residue of the histidine phosphotransfer protein (HPt) which in turn phosphorylates Asp residue in the Response Regulator (RR). The phosphorylated RR protein acts as either a positive or negative transcription factor that interacts with the gene promoter or other target protein. The two-component signaling pathway, operating through the His-Asp phosphorelay, controls many physiological and developmental processes throughout the plant lifecycle (from seed-to-seed). Downstream plant hormone signaling also includes proteolysis of transcriptional regulators that block the activity of transcription factors. Two-component signaling operates more frequently in higher plants. Five classic plant hormones had been discovered by the middle of the twentieth century: auxins, cytokinins, gibberellins, ethylene and abscisic acid. The more recently characterized hormones include brassinosteroids, strigolactones, jasmonates and salicylates. Considering the tremendous work that has been undertaken during the last decades, in this review we decided to concentrate on cytokinin signaling in various plant developmental processes, including responses to biotic and abiotic stresses.

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