A proteomic approach to analyzing responses of Arabidopsis thaliana root cells to different gravitational conditions using an agravitropic mutant, pin2 and its wild type

Abstract

BackgroundRoot gravitropsim has been proposed to require the coordinated, redistribution of the plant signaling molecule auxin within the root meristem, but the underlying molecular mechanisms are still unknown. PIN proteins are membrane transporters that mediate the efflux of auxin from cells. The PIN2 is important for the basipetal transport of auxin in roots and plays a critical role in the transmission of gravity signals perceived in the root cap to the root elongation zone. The loss of function pin2 mutant exhibits a gravity-insensitive root growth phenotype. By comparing the proteomes of wild type and the pin2 mutant root tips under different gravitational conditions, we hope to identify proteins involved in the gravity-related signal transduction.ResultsTo identify novel proteins involved in the gravity signal transduction pathway we have carried out a comparative proteomic analysis of Arabidopsis pin2 mutant and wild type (WT) roots subjected to different gravitational conditions. These conditions included horizontal (H) and vertical (V) clinorotation, hypergravity (G) and the stationary control (S). Analysis of silver-stained two-dimensional SDS-PAGE gels revealed 28 protein spots that showed significant expression changes in altered gravity (H or G) compared to control roots (V and S). Whereas the majority of these proteins exhibited similar expression patterns in WT and pin2 roots, a significant number displayed different patterns of response between WT and pin2 roots. The latter group included 11 protein spots in the H samples and two protein spots in the G samples that exhibited an altered expression exclusively in WT but not in pin2 roots. One of these proteins was identified as annexin2, which was induced in the root cap columella cells under altered gravitational conditions.ConclusionsThe most interesting observation in this study is that distinctly different patterns of protein expression were found in WT and pin2 mutant roots subjected to altered gravity conditions. The data also demonstrate that PIN2 mutation not only affects the basipetal transport of auxin to the elongation zone, but also results in an altered expression of proteins in the root columella.

Spaceflight Induces Specific Alterations in the Proteomes of Arabidopsis

“…While there is not a one-to-one correlation with any gene set from a published spaceflight transcriptome, similar trends in the differential expression of genes important to auxin metabolism, and to a variety of stress responses, can be seen in the transcription profiles from several studies (see citations above). A proteomic survey in terrestrial alteredgravity environments also revealed a host of general stress proteins as well as those associated with auxin signaling (Tan et al, 2011). Although there is little specific overlap with transcriptome studies of plants exposed to similar environments, many of the trends in pathways affected by spaceflight are similar among the studies (Moseyko et al, 2002;Tan et al, 2011).…”

Mechano-biological Coupling of Cellular Responses to Microgravity

“…A recent study indicates that leaf dorsoventral polarity signals lead to mechanical heterogeneity that is sufficient to produce the asymmetry seen in planar leaves via altering cell wall mechanical properties (Qi et al Under review). Altered gravity systems including horizontal and vertical clinorotations, hypergravity, and stationary control are used in studying proteomic responses of Arabidopsis root cells to different gravitational conditions (Tan et al 2011). Comparisons of genomic and proteomic profiles of Arabidopsis and rice callus grown under microgravity on Chinese spacecraft ShenZhou (SZ)-8 with those grown under 1×g centrifugation (1×g control) in space and on ground are also performed (Zhang et al 2015b, c).…”

“…At protein level, the proteomic data of Arabidopsis wildtype (WT) and pin2-mutated root tips and cell cultures under SM or real microgravity conditions indicate that gravity can mediate the expression of particular classes of proteins involved in stress responses such as cytoskeleton organization, metabolic changes in plastids and mitochondria, gene activation/transcription, and cell wall biosynthesis (Tan et al 2011;Qi and Zheng 2013;Zhang et al 2015b, c). Among these gravity-responsible proteins, further attentions are focused on those potentially important proteins involved in the gravity signaling transduction and transmission pathways, such as ANN2, KNAT1, and myosin heavy chain-related protein (MHCRP).…”

“…Among these gravity-responsible proteins, further attentions are focused on those potentially important proteins involved in the gravity signaling transduction and transmission pathways, such as ANN2, KNAT1, and myosin heavy chain-related protein (MHCRP). It is noticed that ANN2 could interact with MHCRP and regulate the early response of roots to the gravitational stimulation (Tan et al 2011) via affecting the reorganization of actin-network in columella cells. This is further confirmed by the observation of differential increase of ANN2-GFP signals in the columella cells of WT or pin2-mutated plants subjected to SM.…”

Performance of Phaseolus vulgaris under partial root-zone drying cultivated in a hydrogravitropic system response

“…Por otro lado, la capacidad de las raíces de las plantas para reconocer pequeños cambios en los patrones de humedad del suelo (Robbins y Dinneny, 2015), les permite sopesar los riesgos de aversión y propensión para activar su crecimiento (Dener et al, 2016). En este sentido, el conjunto de experiencias que ha permitido comprender las respuestas de las raíces a las señales abióticas, donde estas orientan su crecimiento, principalmente, por la influencia del vector gravitatorio de la Tierra o gravitropismo (Tan et al, 2011), y por la presencia de gradientes hídricos en el suelo o hidrotropismo (Moriwaki, et al, 2013), constituyen fenómenos físicos que pueden ser considerados en el diseño y construcción de sistemas geométricos que aprovechen mejor la capacidad de las raíces para distribuirse tridimensionalmente en el suelo (Vega, 2017). De esta forma, el macetero de respuesta hidrogravitrópica es una solución física que permite perfeccionar el manejo del riego parcial de raíces, pues se obtiene un mayor control de la aplicación del agua, respecto a la configuración geométrica del macetero, realizada por Puértolas et al (2015) en las experiencias con similar técnica de riego.…”