In Plants, 3-O-Methylglucose Is Phosphorylated by Hexokinase But Not Perceived as a Sugar

Abstract

The dynamics of polyribosome abundance were studied in gravistimulated maize (Zea mays) stem pulvini. During the initial 15 min of gravistimulation, the amount of large polyribosomes transiently decreased. The transient decrease in polyribosome levels was accompanied by a transient decrease in polyribosome-associated mRNA. After 30 min of gravistimulation, the levels of polyribosomes and the amount of polyribosome-associated mRNA gradually increased over 24 h up to 3-to 4-fold of the initial value. Within 15 min of gravistimulation, total levels of transcripts coding for calreticulin and calmodulin were elevated 5-fold in maize pulvinus total RNA. Transcripts coding for calreticulin and calmodulin were recruited into polyribosomes within 15 min of gravistimulation. Over 4 h of gravistimulation, a gradual increase in the association of calreticulin and calmodulin transcripts with polyribosomes was seen predominantly in the lower one-half of the maize pulvinus; the association of transcripts for vacuolar invertase with polyribosomes did not change over this period. Our results suggest that within 15 min of gravistimulation, the translation of the majority of transcripts associated with polyribosomes decreased, resembling a general stress response. Recruitment of calreticulin and calmodulin transcripts into polyribosomes occurred predominantly in the lower pulvinus one-half during the first 4 h when the presentation time for gravistimulation in the maize pulvinus is not yet complete.The vector of the gravitational force provides a constant cue for the direction of plant growth. Changes in the orientation of a plant relative to the gravity vector result in positive or negative gravitropic growth of roots and shoots, respectively. The gravity vector is thought to be perceived through changes in tensegrity or the pressure exerted by statoliths (Sack, 1991; Kaufman et al., 1995;Yoder et al., 2001) or by the entire protoplast (Staves, 1997). Sedimentation of statoliths in starch-containing cells can occur within seconds to minutes of gravistimulation (Sack, 1991; Kaufman et al., 1995;Yoder et al., 2001). A cascade of coordinated biochemical events subsequently amplifies and distributes the signal through a responsive tissue, resulting in the redistribution of auxin between upper and lower sides of the gravistimulated organ and initiating the bending response (for review, see Kaufman et al., 1995; Lomax et al., 1995;Sinclair and Trewavas, 1997;Chen et al., 1999;Rosen et al., 1999). Although the gravitropic response of plants has been the subject of intensive research, our understanding of the signaling processes linking perception of gravity to differential growth is still limited.The stem pulvini of cereal grasses have previously been used as model systems for the investigation of gravitropic growth in a number of studies (Dayanandan and Kaufman, 1984; Kaufman et al., 1987 Kaufman et al., , 1995Winter et al., 1997; Collings et al., 1998;Perera et al., 1999Perera et al., , 2001 Johannes et al., 2001). The pulvini are d...

Phosphate starvation responses are mediated by sugar signaling in Arabidopsis

“…The variable eVects of sugars and its analogs on the expression of diVerent genes could be attributed to the activation of diVerent components of sugar mediated signaling pathways (Sinha et al 2002). Although palatinose and turonose are not transported, 3-OMG, which is transported across the membrane (Cortes et al 2003) and can regulate the expression of (c, d). Samples were harvested 1, 3, 6, 12, 24, 48 or 72 h after transfer.…”

A Universal Role for Inositol 1,4,5-Trisphosphate-Mediated Signaling in Plant Gravitropism

“…Very rapid gravity-specific changes in transcript abundance have been documented in gravistimulated root tips of Arabidopsis (Arabidopsis thaliana; Kimbrough et al, 2004) and in whole seedlings (Moseyko et al, 2002). Additionally, Heilmann et al (2001) have demonstrated that specific transcripts are selectively recruited into polysomes of maize (Zea mays) pulvini within 15 to 30 min of gravistimulation, and Young and Masson (2004) have shown that rapid changes in protein distribution occur within 12 to 30 min of gravistimulation in Arabidopsis roots. These results indicate that transcriptional and translational regulation is also involved in the early signaling events.…”

A Computational and Experimental Approach Reveals that the 5′-Proximal Region of the 5′-UTR has a Cis-Regulatory Signature Responsible for Heat Stress-Regulated mRNA Translation in Arabidopsis

“…Previous gene-specific and genome-wide studies of translational control make it increasingly clear that differential translation of mRNA species occurs in plants under a range of situations, including abiotic stresses (Kawaguchi et al 2004, Branco-Price et al 2008, Matsuura et al 2010, changes in light availability (Juntawong and Bailey-Serres 2012) and gravistimulation (Heilmann et al 2001). Differential translation also occurs among distinct cell types (Mustroph et al 2009) and among different stages of plant development (Jiao andMeyerowitz 2010, Liu et al 2012).…”