Hypocotyl

About: Hypocotyl is a research topic. Over the lifetime, 2888 publications have been published within this topic receiving 67281 citations.

Soybean transformation and regeneration methods

Abstract: A method of transforming and regenerating soybean plants relies on selection of hypocotyl explants as the target material. Hypocotyl explants can be transformed either by microparticle bombardment with DNA-coated microparticles of inert metals, or by co-culturing with an Agrobacterium strain. The transformed explants can be successfully regenerated, using a protocol including culturing on a shoot induction medium, followed by transfer to a shoot elongation medium to form rooted plantlets, which are transplanted to soil.

Genetic Control of Light-inhibited Hypocotyl Elongation in Arabidopsis thaliana (L.) Heynh

Abstract: Summary Reduced sensitivity to the inhibitory action of white light on hypocotyl elongation was observed in 41 mutants induced in Arabidopsis tbaliana at 5 different loci. Compared to wild type, these mutants show a locus-specific altered inhibition spectrum when grown in light of restricted spectral regions. Spectrophotometrically detectable phytochrome in dark-grown tissue of those mutants (loci by-1 and by-2) in which the inhibitory effect of far red light is almost or completely absent, is either greatly reduced or below the level of detectability. The spectra of the different mutants and their recombinants provide evidence for the presence of more than one photoreceptor pigment for the High Irradiance Reaction and demonstrate the genetic control of light-induced inhibition of hypocotyl growth.

Nitric oxide stimulates seed germination and de-etiolation, and inhibits hypocotyl elongation, three light-inducible responses in plants

Abstract: Seed germination, greening of etiolated plants and inhibition of hypocotyl elongation are stimulated by light, which is sensed by various types of photoreceptor. Nitric oxide (NO) has proven to be a bioactive molecule, especially in mammalian cells and, most recently, in plants. Like some phytochrome-dependent processes, many NO-mediated ones are accomplished through increases in cGMP levels. Given these similarities, we proposed that NO could take part in light-mediated events in plants. Here we show that NO promotes seed germination and de-etiolation, and inhibits hypocotyl and internode elongation, processes mediated by light. Two NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine induced germination of lettuce (Lactuca sativa L. cv. Grand Rapids) seeds in conditions in which this process is dependent on light (e.g. 26 °C). This was a dose-dependent response and was arrested by addition of an NO scavenger, carboxy-PTIO. In addition, nitrite and nitrate, two NO-decomposition products were ineffective in stimulating germination. Wheat seedlings sprayed with SNP and grown in darkness contained 30–40% more chlorophyll than control seedlings. Nitric-oxide-mediated partial greening was increased by light pulses, wounding and biotic stress. Arabidopsis thaliana (L.) Heynh. (ecotype Columbia) and lettuce seedlings grown in the dark had 20%-shorter hypocotyls in NO treatments than in control ones. On the other hand, internode lengths of potato plants growing under low light intensity and sprayed with 100 μM SNP were also 20% shorter than control ones. These results implicate NO as a stimulator molecule in plant photomorphogenesis, either dependent on or independent of plant photoreceptors.

Cellular basis of hypocotyl growth in Arabidopsis thaliana.

Abstract: The Arabidopsis thaliana hypocotyl is widely used to study the effects of light and plant growth factors on cell elongation. To provide a framework for the molecular-genetic analysis of cell elongation in this organ, here we describe, at the cellular level, its morphology and growth and identify a number of characteristic, developmental differences between light-grown and dark-grown hypocotyls. First, in the light epidermal cells show a characteristic differentiation that is not observed in the dark. Second, elongation growth of this organ does not involve significant cortical or epidermal cell divisions. However, endoreduplication occurs, as revealed by the presence of 4C and 8C nuclei. In addition, 16C nuclei were found specifically in dark-grown seedlings. Third, in the dark epidermal cells elongate along a steep, acropetal spatial and temporal gradient along the hypocotyl. In contrast, in the light all epidermal cells elongated continuously during the entire growth period. These morphological and physiological differences, in combination with previously reported genetic data (T. Desnos, V. Orbovic, C. Bellini, J. Kronenberger, M. Caboche, J. Traas, H. Hofte [1996] Development 122: 683-693), illustrate that light does not simply inhibit hypocotyl growth in a cell-autonomous fashion, but that the observed growth response to light is a part of an integrated developmental change throughout the elongating organ.

High temperature promotes auxin-mediated hypocotyl elongation in Arabidopsis.

Abstract: Physiological studies with excised stem segments have implicated the plant hormone indole-3-acetic acid (IAA or auxin) in the regulation of cell elongation. Supporting evidence from intact plants has been somewhat more difficult to obtain, however. Here, we report the identification and characterization of an auxin-mediated cell elongation growth response in Arabidopsis thaliana. When grown in the light at high temperature (29°C), Arabidopsis seedlings exhibit dramatic hypocotyl elongation compared with seedlings grown at 20°C. This temperature-dependent growth response is sharply reduced by mutations in the auxin response or transport pathways and in seedlings containing reduced levels of free IAA. In contrast, mutants deficient in gibberellin and abscisic acid biosynthesis or in ethylene response are unaffected. Furthermore, we detect a corresponding increase in the level of free IAA in seedlings grown at high temperature, suggesting that temperature regulates auxin synthesis or catabolism to mediate this growth response. Consistent with this possibility, high temperature also stimulates other auxin-mediated processes including auxin-inducible gene expression. Based on these results, we propose that growth at high temperature promotes an increase in auxin levels resulting in increased hypocotyl elongation. These results strongly support the contention that endogenous auxin promotes cell elongation in intact plants.