Abscisic acid is a negative regulator of root gravitropism in Arabidopsis thaliana

Auh

et al. 2011

Planta

Seedlings of Arabidopsis thaliana (cv. Columbia) were used to evaluate dynamic transcriptional-level genome responses to simulated microgravity condition created by 3-D clinorotation. The DNA chip data analysis showed that the plant may respond to simulated microgravity by dynamic induction (up- and down-regulations) of the responsive genes in the genome. The qRT-PCR results on the investigated genes showed that the expression patterns of the genes (molecular response) were generally similar to the physiological response patterns detected in stress-challenged plants. Expression patterns were categorized into short or continual up- or down-regulated patterns, as well as stochastic changes from short- to long-term simulated microgravity stress. The induced genes are then assumed to establish a new molecular plasticity to the newly adjusted genome status in the basic milieu of maintaining homeostasis during the process of adaptation to simulated microgravity.

Section: Abf3mentioning

confidence: 99%

Gene expression changes in Arabidopsis seedlings during short- to long-term exposure to 3-D clinorotation

Auh

et al. 2011

Planta

“…Studies have reported that the root gravitropic response of the pldf2 mutant is retarded compared with that of wild-type roots and that exogenous ABA affects gravitropism in wild-type roots (Han et al 2009). Hence, we next examined root gravitropism in the pldf2 mutant in the presence of exogenous ABA.…”

Section: Aba Enhanced the Pldf2 Promoter Activity In Root Capsmentioning

confidence: 98%

Involvement of Arabidopsis thaliana phospholipase Dζ2 in root hydrotropism through the suppression of root gravitropism

Taniguchi

Tsuge

et al. 2009

Planta

Root hydrotropism is the phenomenon of directional root growth toward moisture under water-deficient conditions. Although physiological and genetic studies have revealed the involvement of the root cap in the sensing of moisture gradients, and those of auxin and abscisic acid (ABA) in the signal transduction for asymmetric root elongation, the overall mechanism of root hydrotropism is still unclear. We found that the promoter activity of the Arabidopsis phospholipase Dzeta2 gene (PLDzeta2) was localized to epidermal cells in the distal root elongation zone and lateral root cap cells adjacent to them, and that exogenous ABA enhanced the activity and extended its area to the entire root cap. Although pldzeta2 mutant root caps did not exhibit a morphological phenotype in either the absence or presence of exogenous ABA, the inhibitory effect of ABA on gravitropism, which was significant in wild-type roots, was not observed in pldzeta2 mutant roots. In root hydrotropism experiments, pldzeta2 mutations significantly retarded or disturbed root hydrotropic responses. A drought condition similar to that used in a hydrotropism experiment enhanced the PLDzeta2 promoter activity in the root cap, as did exogenous ABA. These results suggest that PLDzeta2 responds to drought through ABA signaling in the root cap and accelerates root hydrotropism through the suppression of root gravitropism.

Encyclopedia of Life Sciences

“…See also: Cytokinins A role for ABA in gravitropic response is controversial (Moore, 1990;Young and Evans, 1996) and there is evidence for this hormone acting to antagonise auxin during root gravitropism (e.g. Han et al, 2009). Similarly, jasmonates, brassinosteroids and ethylene have all been proposed to play roles in modulating auxin responsiveness during the graviresponse (e.g.…”

Section: Auxin and The Regulation Of Growthmentioning

confidence: 99%

Gravitropic Signaling in Plants

Gilroy

Swanson

2014

The direction of gravity represents a fundamental signal that plants use to shape their growth and development. In the simplest description of this phenomenon, roots grow down and shoots grow up; however, closer examination reveals that different plant organs such as the individual branches of a tree, maintain different angles to gravity, their ‘gravitropic set‐point angle’. When displaced from this orientation, plant organs have the ability to redirect growth to regain their preferred angle through the process of gravitropism. The starch‐statolith hypothesis describes the cellular mechanism whereby plants can sense the direction of gravity and so regulate growth in response to this signal. The sedimentation of dense starch‐filled amyloplasts within specialised sensory cells is thought to generate an as yet undefined directional biochemical signal. This signalling system then modulates transport of the plant hormone auxin resulting in its accumulation and the localisation of growth that leads to the gravitropic response. Key Concepts: Plants sense the direction of gravity and regulate growth of roots and shoots using this information. Directional growth in response to gravity is known as gravitropism. Different organs can use gravitropism to maintain different genetically defined angles, or gravitropic set‐point angles, relative to the gravity vector. Sensing the direction of gravity is achieved by dense starch‐filled amyloplasts sedimenting in specialised sensory cells, called statocytes. The statocytes are the columella cells of the root cap and the endodermal cells in the shoot. Sedimentation of amyloplasts generates an initial biochemical signal within the statocytes that has yet to be defined. Signalling within the statocytes triggers redistribution of transporters for the hormone auxin to the plasma membrane on the lower side of the cell. Asymmetrical activity of auxin transport causes this hormone to accumulate on the lower side of the root or shoot. Auxin promotes cell elongation in shoots and inhibits this process in roots. Differential cell elongation between one side of an organ and the other causes the root to bend downwards and the shoot upwards.