Short Peptides Induce Development of Root Hair Nicotiana tabacum

Root hairs absorb soil nutrients and water, and anchor the plant in the soil. Treatment of tobacco (Nicotiana tabacum) roots with glycine (Gly) amino acid, and glycilglycine (GlyGly) and glycilaspartic acid (GlyAsp) dipeptides (10⁻⁷ M concentration) significantly increased the development of root hairs. In the root, peptide accumulation was tissue-specific, with predominant localization to the root cap, meristem, elongation zone, and absorption zone. Peptides penetrated the epidermal and cortical cell and showed greater localization to the nucleus than to the cytoplasm. Compared with the control, tobacco plants grown in the presence of Gly, GlyGly, and GlyAsp exhibited the activation of WER, CPC, bHLH54, and bHLH66 genes and suppression of GTL1 and GL2 genes during root hair lengthening. Although Gly, GlyGly, and GlyAsp have a similar structure, the mechanism of regulation of root hair growth in each case were different, and these differences are most likely due to the fact that neutral Gly and GlyGly and negatively charged GlyAsp bind to different motives of functionally important proteins. Short peptides site-specifically interact with DNA, and histones. The molecular mechanisms underlying the effect of exogenous peptides on cellular processes remain unclear. Since these compounds acted at low concentrations, gene expression regulation by short peptides is most likely of epigenetic nature.

Transcriptomic Analysis of the Host Response to Mild and Severe CTV Strains in Naturally Infected Citrus sinensis Orchards

Citrus tristeza virus (CTV) is an important threat to the global citrus industry, causing severe economic losses worldwide. The disease management strategies are focused on vector control, tree culling, and the use of resistant varieties and rootstocks. Sweet orange (Citrus sinensis) trees showing either severe or mild CTV symptoms have been observed in orchards in Veracruz, Mexico, and were probably caused by different virus strains. To understand these symptomatic differences, transcriptomic analyses were conducted using asymptomatic trees. CTV was confirmed to be associated with infected plants, and mild and severe strains were successfully identified by a polymorphism in the coat protein (CP) encoding gene. RNA-Seq analysis revealed more than 900 significantly differentially expressed genes in response to mild and severe strains, with some overlapping genes. Importantly, multiple sequence reads corresponding to Citrus exocortis viroid and Hop stunt viroid were found in severe symptomatic and asymptomatic trees, but not in plants with mild symptoms. The differential gene expression profiling obtained in this work provides an overview of molecular behavior in naturally CTV-infected trees. This work may contribute to our understanding of citrus-virus interaction in more natural settings, which can help develop strategies for integrated crop management.