(Not) Keeping the stem straight: a proteomic analysis of maritime pine seedlings undergoing phototropism and gravitropism

Abstract

BackgroundPlants are subjected to continuous stimuli from the environment and have evolved an ability to respond through various growth and development processes. Phototropism and gravitropism responses enable the plant to reorient with regard to light and gravity.ResultsWe quantified the speed of maritime pine seedlings to reorient with regard to light and gravity over 22 days. Seedlings were inclined at 15, 30 and 45 degrees with vertical plants as controls. A lateral light source illuminated the plants and stem movement over time was recorded. Depending on the initial angle of stem lean, the apical response to the lateral light source differed. In control and 15° inclined plants, the apex turned directly towards the light source after only 2 h. In plants inclined at 30° and 45°, the apex first reoriented in the vertical plane after 2 h, then turned towards the light source after 24 h. Two-dimensional gel electrophoresis coupled with mass spectrometry was then used to describe the molecular response of stem bending involved in photo- and gravi-tropism after 22 hr and 8 days of treatment. A total of 486 spots were quantitatively analyzed using image analysis software. Significant changes were determined in the protein accumulation of 68 protein spots. Early response gravitropic associated proteins were identified, which are known to function in energy related and primary metabolism. A group of thirty eight proteins were found to be involved in primary metabolism and energy related metabolic pathways. Degradation of Rubisco was implicated in some protein shifts.ConclusionsOur study demonstrates a rapid gravitropic response in apices of maritime pine seedlings inclined >30°. Little or no response was observed at the stem bases of the same plants. The primary gravitropic response is concomitant with a modification of the proteome, consisting of an over accumulation of energy and metabolism associated proteins, which may allow the stem to reorient rapidly after bending.

Transcriptome profiling of peanut (Arachis hypogaea) gynophores in gravitropic response

“…Among the metabolism pathways identified, carbohydrate metabolism and amino acid metabolism are the two major pathways, following with energy metabolism, biosynthesis of other secondary metabolites, metabolism of terpenoids and polyketides, glycan biosynthesis and metabolism, and nucleotide metabolism. Similar to our results, transcriptome analysis in Arabidopsis exposed to gravity stimulation also revealed that metabolism is one of major gene groups responding to gravitropism (Kimbrough et al 2004;Kittang et al 2004) Among the metabolism pathways identified in this study, energy metabolism was also found to function in plants under gravitropic stimulation according to proteomic analysis (Azri et al 2009;Herrera et al 2010). In Arabidopsis, secondary metabolism genes were altered by magnetically induced hyperand microgravity at both transcription and translation levels (Manzano et al 2012;Herranz et al 2013).…”

Is the Responsiveness to Light Related to the Differences in Stem Straightness among Populations of Pinus pinaster?

“…Herrera et al [42] reported an alternative priority in the gravi- and phototropic reactions of P. pinaster seedlings under different levels of tilting and simultaneous lateral illumination: The plants tilted 30° or more had an immediate vertical primary reaction and then turned toward the light, while the plants tilted 0° and 15° directly turned to the light. In our experiment, a vertical reaction of the apex (primary gravitropic response) did not occur, but fluctuations of the leaning angles could respond to the alternative priorities involving both primary and secondary reactions.…”

Peg Biology: Deciphering the Molecular Regulations Involved During Peanut Peg Development

“…Recently, a proteomic study of pine and poplar has also suggested the role of class III acidic endochitinases during gravitropic response. These genes are associated with carbohydrate metabolism, and are also storage proteins (Azri et al, 2009; Herrera et al, 2010), residing at the starch granules of the amyloplast, which is known to be involved in sensing the direction of gravity to promote downward gravitropic curvature (Lv et al, 2011). In plants, carbonic anhydrases are also involved in carbohydrate metabolism and photomorphogenesis (Wang et al, 2012).…”