Glucose and Auxin Signaling Interaction in Controlling Arabidopsis thaliana Seedlings Root Growth and Development

Abstract

BackgroundPlant root growth and development is highly plastic and can adapt to many environmental conditions. Sugar signaling has been shown to affect root growth and development by interacting with phytohormones such as gibberellins, cytokinin and abscisic acid. Auxin signaling and transport has been earlier shown to be controlling plant root length, number of lateral roots, root hair and root growth direction.Principal FindingsIncreasing concentration of glucose not only controls root length, root hair and number of lateral roots but can also modulate root growth direction. Since root growth and development is also controlled by auxin, whole genome transcript profiling was done to find out the extent of interaction between glucose and auxin response pathways. Glucose alone could transcriptionally regulate 376 (62%) genes out of 604 genes affected by IAA. Presence of glucose could also modulate the extent of regulation 2 fold or more of almost 63% genes induced or repressed by IAA. Interestingly, glucose could affect induction or repression of IAA affected genes (35%) even if glucose alone had no significant effect on the transcription of these genes itself. Glucose could affect auxin biosynthetic YUCCA genes family members, auxin transporter PIN proteins, receptor TIR1 and members of a number of gene families including AUX/IAA, GH3 and SAUR involved in auxin signaling. Arabidopsis auxin receptor tir1 and response mutants, axr2, axr3 and slr1 not only display a defect in glucose induced change in root length, root hair elongation and lateral root production but also accentuate glucose induced increase in root growth randomization from vertical suggesting glucose effects on plant root growth and development are mediated by auxin signaling components.ConclusionOur findings implicate an important role of the glucose interacting with auxin signaling and transport machinery to control seedling root growth and development in changing nutrient conditions.

The Pitfalls of Transgenic Selection and New Roles ofAtHXK1: A High Level ofAtHXK1Expression Uncouples Hexokinase1-Dependent Sugar Signaling from Exogenous Sugar

“…These effects of AtHXK1 on auxin-related genes differ from previously published results showing that an auxin response is essential for AtHXK1-mediated sugar inhibition of seedling growth on 6% Glc (Moore et al, 2003). They are also in contrast to results showing increased expression of PIN1 in whole seedlings kept in the dark and exposed to 3% Glc for 3 h (Mishra et al, 2009). However, the observed effects are in line with the observation of reduced expression of TIR1 in response to the same Glc treatment (Mishra et al, 2009).…”

“…They are also in contrast to results showing increased expression of PIN1 in whole seedlings kept in the dark and exposed to 3% Glc for 3 h (Mishra et al, 2009). However, the observed effects are in line with the observation of reduced expression of TIR1 in response to the same Glc treatment (Mishra et al, 2009). Hence, it appears that Glc and AtHXK1 interact with auxin in a complicated manner that depends on growth conditions, the tissue examined, and the developmental stage of the plant.…”

Haustorial Hairs Are Specialized Root Hairs That Support Parasitism in the Facultative Parasitic Plant Phtheirospermum japonicum

“…HHD1 controls root hair initiation and elongation, while HHD2 regulates elongation but not initiation. In Arabidopsis, the GL2, AXR3, RHL1/2/3, RHD6, and CPC genes regulate root hair initiation (Masucci and Schiefelbein, 1994;Masucci et al, 1996;Schneider et al, 1997;Schellmann et al, 2002;Mishra et al, 2009). Most of the mutations in these genes produce additional defects in root hair elongation, resembling the root hair phenotypes of hhd1-1 and hhd1-2.…”

Cytokinin Interplay with Ethylene, Auxin, and Glucose Signaling Controls Arabidopsis Seedling Root Directional Growth

“…For example, Glc interacts with CK and auxin to control the cell cycle (Riou-Khamlichi et al, 2000;Hartig and Beck, 2006). Glc affects ethylene signaling (Leó n and Sheen, 2003) and auxin signaling/transport (Mishra et al, 2009); thus, the mechanism of the Glc effect on CK signaling here may be direct or by modulating ethylene and auxin signaling/transport. Since ACC and IAA at similar concentrations did not cause a similar response as CK did in Glc-containing medium (Fig.…”

“…The increasing Glc concentration not only increases root length, number of lateral roots, and root hairs but also modulates the gravitropic response of the primary roots of young seedlings (Mishra et al, 2009). Increasing Glc concentrations can induce differential root length, lateral roots, gravitropism, and root hair elongation in auxin perception and signaling mutants, suggesting that auxin signaling is involved in controlling Glc-regulated root responses (Mishra et al, 2009). Glc has also been shown to act via G-protein signaling to attenuate auxin-mediated bimodality in controlling lateral root formation (Booker et al, 2010).…”