The root is the below-ground organ of a plant, and it has evolved multiple signaling pathways that allow adaptation of architecture, growth rate, and direction to an ever-changing environment. Roots grow along the gravitropic vector towards beneficial areas in the soil to provide the plant with proper nutrients to ensure its survival and productivity. In addition, roots have developed escape mechanisms to avoid adverse environments, which include direct illumination. Standard laboratory growth conditions for basic research of plant development and stress adaptation include growing seedlings in Petri dishes on medium with roots exposed to light. Several studies have shown that direct illumination of roots alters their morphology, cellular and biochemical responses, which results in reduced nutrient uptake and adaptability upon additive stress stimuli. In this review, we summarize recent methods that allow the study of shaded roots under controlled laboratory conditions and discuss the observed changes in the results depending on the root illumination status.

• Keywords
• D-rootsystem, abiotic stress, auxin, cytokinin, dark-grown roots, direct root illumination, flavonols, light escape mechanism, reactive oxygen species, root growth,
• MeSH
• Adaptation, Physiological * MeSH
• Plant Roots metabolism   radiation effects   MeSH
• Gene Expression Regulation, Plant radiation effects   MeSH
• Plant Proteins genetics   metabolism   MeSH
• Plants metabolism   radiation effects   MeSH
• Seedlings metabolism   radiation effects   MeSH
• Light * MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Plant Proteins MeSH

Salt and osmotic stress are the main abiotic stress factors affecting plant root growth and architecture. We investigated the effect of salt (100 mM NaCl) and osmotic (200 mM mannitol) stress on the auxin metabolome by UHPLC-MS/MS, auxin distribution by confocal microscopy, and transcript levels of selected genes by qRT-PCR in Arabidopsis thaliana ecotype Columbia-0 (Col-0) and DR5rev::GFP (DR5) line. During long-term stress (13 days), a stability of the auxin metabolome and a tendency to increase indole-3-acetic acid (IAA) were observed, especially during salt stress. Short-term stress (3 h) caused significant changes in the auxin metabolome, especially NaCl treatment resulted in a significant reduction of IAA. The data derived from auxin profiling were consistent with gene expressions showing the most striking changes in the transcripts of YUC, GH3, and UGT transcripts, suggesting disruption of auxin biosynthesis, but especially in the processes of amide and ester conjugation. These data were consistent with the auxin distribution observed in the DR5 line. Moreover, NaCl treatment caused a redistribution of auxin signals from the quiescent center and the inner layers of the root cap to the epidermal and cortical cells of the root elongation zone. The distribution of PIN proteins was also disrupted by salt stress; in particular, PIN2 was suppressed, even after 5 min of treatment. Based on our results, the DR5 line was more sensitive to the applied stresses than Col-0, although both lines showed similar trends in root morphology, as well as transcriptome and metabolome parameters under stress conditions.

• Keywords
• Arabidopsis thaliana, abiotic stress, auxin distribution, auxin metabolome, auxin transcriptome, root growth,
• MeSH
• Arabidopsis growth & development   MeSH
• Sodium Chloride pharmacology   MeSH
• Plant Roots growth & development   MeSH
• Indoleacetic Acids metabolism   MeSH
• Arabidopsis Proteins biosynthesis   MeSH
• Gene Expression Regulation, Plant drug effects   MeSH
• Salt Stress drug effects   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Sodium Chloride MeSH
• Indoleacetic Acids MeSH
• Arabidopsis Proteins MeSH

Embryogenesis in seed plants is the process during which a single cell develops into a mature multicellular embryo that encloses all the modules and primary patterns necessary to build the architecture of the new plant after germination. This process involves a series of cell divisions and coordinated cell fate determinations resulting in the formation of an embryonic pattern with a shoot-root axis and cotyledon(s). The phytohormone auxin profoundly controls pattern formation during embryogenesis. Auxin functions in the embryo through its maxima/minima distribution, which acts as an instructive signal for tissue specification and organ initiation. In this review, we describe how disruptions of auxin biosynthesis, transport, and response severely affect embryo development. Also, the mechanism of auxin action in the development of the shoot-root axis and the three-tissue system is discussed with recent findings. Biological tools that can be implemented to study the auxin function during embryo development are presented, as they may be of interest to the reader.

• MeSH
• Biological Transport MeSH
• Plant Roots growth & development   MeSH
• Indoleacetic Acids metabolism   MeSH
• Plant Growth Regulators metabolism   MeSH
• Seeds growth & development   MeSH
• Signal Transduction MeSH
• Plant Shoots growth & development   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Plant Growth Regulators MeSH

Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less attention in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely disrupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased transport of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1 ovules. These observations suggest that communication between the sporophyte and the developing female gametophyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule.

• Keywords
• Arabidopsis, PIN1, PIN3, Rab, auxin transport, female gametophyte, funiculus, ovule, rab geranylgeranyl transferase,
• MeSH
• Arabidopsis * genetics   MeSH
• Indoleacetic Acids MeSH
• Arabidopsis Proteins * genetics   MeSH
• Pollen Tube MeSH
• Ovule genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Indoleacetic Acids MeSH
• Arabidopsis Proteins * MeSH