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Query: UNIPROT:P50583 (
asymmetrical
)
12,197
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Culture of isolated microspores and of anthers on media containing
IAA
directed free microspore development to an embryogenic pathway in C. olitorius. The first division of microspores on transfer to culture media was symmetrical in contrast to the
asymmetrical
division seen in normal development in vivo. Initially, 10-30% microspores divided symmetrically, but only 0.2-1% of the dividing microspores continued dividing and produced multicellular microcalli. About 30% of these microcalli produced callus but only on medium with 2.0 mg/L zeatin and 0.1 mg/L
IAA
. Incubation in the dark at temperatures of 35 degrees C for 1 day and then 25 degrees C was found effective for induction of first embryonic division in Corchorus. The frequency of microspore callus formation was higher on medium containing either 3% or 5% sucrose. Addition of colchicine and addition of activated charcoal to the above medium did not enhance microspore division in Corchorus olitorius. On transfer to different media most calli produced roots but regeneration of shoots and embryos was not induced.
...
PMID:Microspore culture in Corchorus olitorius: effect of growth regulators, temperature and sucrose on callus formation. 1111 31
The negative gravitropic response of cut flower stalks is a complex multistep process that requires the participation of various cellular components acting in succession or in parallel. The process was particularly characterized in snapdragon (Antirrhinum majus L.) spikes with regard to (1) gravity stimulus perception associated with amyloplast reorientation; (2) stimulus transduction mediated through differential changes in the level, action and related genes of auxin and ethylene and their possible interaction; (3) stimulus response associated with differential growth leading to stalk curvature; (4) involvement of cytosolic calcium and actin cytoskeleton. Results show that the gravity-induced amyloplast reorientation, differential over-expression of two early auxin responsive genes and
asymmetrical
distribution of free
IAA
are early events in the bending process. These precede the
asymmetrical
ethylene production and differential stem growth, which was derived from initial shrinkage of the upper stem side and a subsequent elongation of the lower stem side. Results obtained with various calcium- and cytoskeleton-related agents indicate that cytosolic calcium and actin filaments may play essential roles in gravitropism-related processes of cut flower stalks. Therefore, modulators of these two physiological mediators may serve as means for controlling any undesired gravitropic bending.
...
PMID:Gravitropism in cut flower stalks of snapdragon. 1159 35
The models explaining root gravitropism propose that the growth response of plants to gravity is regulated by asymmetric distribution of auxin (indole-3-acetic acid,
IAA
). Since cytokinin has a negative regulatory role in root growth, we suspected that it might function as an inhibitor of tropic root elongation during gravity response. Therefore, we examined the free-bioactive-cytokinin-dependent ARR5::GUS expression pattern in root tips of transformants of Arabidopsis thaliana (L.) Heynh., visualized high cytokinin concentrations in the root cap with specific monoclonal antibodies, and complemented the analyses by external application of cytokinin. Our findings show that mainly the statocytes of the cap produce cytokinin, which may contribute to the regulation of root gravitropism. The homogenous symmetric expression of the cytokinin-responsive promoter in vertical root caps rapidly changed within less than 30 min of gravistimulation into an
asymmetrical
activation pattern, visualized as a lateral, distinctly stained, concentrated spot on the new lower root side of the cap cells. This asymmetric cytokinin distribution obviously caused initiation of a downward curvature near the root apex during the early rapid phase of gravity response, by inhibiting elongation at the lower side and promoting growth at the upper side of the distal elongation zone closely behind the root cap. Exogenous cytokinin applied to vertical roots induced root bending towards the application site, confirming the suspected inhibitory effect of cytokinin in root gravitropism. Our results suggest that the early root graviresponse is controlled by cytokinin. We conclude that both cytokinin and auxin are key hormones that regulate root gravitropism.
...
PMID:Role of cytokinin in the regulation of root gravitropism. 1536 40
Differential growth responses of primary Zea mays L. roots were induced after
asymmetrical
applications of
IAA
-loaded beads along their elongating zone (1.0-4.0 mm from tip) and were modulated according to the initial growth rates of the roots. The amplitude and location (midpoint) of curvature, the elongation of the roots and the uptake of
IAA
were measured after 4 h. The amount of curvature depended on the location of the bead and upon the amount of
IAA
taken up. Curvature occurred towards the site of
IAA
application and the zone (midpoint) of curvature was always found to be basipetal to the
IAA
-loaded bead, indicating the transport of a growth signal in a basipetal direction from the zone of
IAA
application towards the zone of curvature. Two regions within the elongation zone were thus characterized: an acropetal region (between 1.0-3.5 mm from the tip) in which
IAA
induced a growth signal and a basipetal region (3.5-6.5 mm from the tip) which displayed the growth response; neither of these regions were able to carry out both physiological functions. The acropetal region was extended in fast-growing roots or when the amount of applied
IAA
was increased. No significant growth stimulation of fast-growing roots was induced regardless of the amount of
IAA
supplied, but the growth of slow-growing roots was stimulated with very low amounts of
IAA
([Symbol: see text]100 pg/root after 4 h). Inhibition of growth of both classes of roots increased with amounts of
IAA
between 100-600 pg/root after 4 h, but no further inhibition of growth appeared after treatment with greater amounts of
IAA
. A model based on these data shows a possible relationship between the uptake of
IAA
and root growth and indicates a clear relationship between an optimal level of
IAA
and root growth. The responses of the elongating cells of primary maize roots to applied
IAA
depend on their developmental stage and on the initial growth rates of the root.
...
PMID:Local treatment with indole-3-acetic acid induces differential growth responses in Zea mays L. roots. 2418 80
Under light, some growth inhibiting substances were produced in the root cap of maize; they moved basipetally from the tip to the extending zone. An
asymmetrical
uptake by the root stumps of these inhibitors induced a curvature of the root segments. Evidence was given that these growth regulators, formed in the root cap on exposure to light, can cause root curvature in darkness. Assays with two varieties of maize (Anjou which is georeactive both in dark and in light, and Kelvedon georeacting in light only) and with
IAA
-applied on the basal cut end of the root segments-were discussed in relation to the light effect on the formation of the cap growth factors. Experiments involving use of ABA-which has some growth properties identical to those of these inhibitors-lead to the conclusion that the light was only acting on the formation, in the root, of the growth-inhibiting substances. But light seems not to have an effect on the transport of these inhibitors from the cap to the stump or on their action on the elongating part of the roots.
...
PMID:The light effect on the growth inhibitors produced by the root cap. 2442 35
Hydrogen peroxide (H
2
O
2
) is the key factor in many physiological and metabolic processes in plants. During seed germination, exogenous H
2
O
2
application influences gravitropism and induces curvature of the primary root in grass pea and pea seedlings. However, it remains unclear whether and how this happens in the model plant Arabidopsis thaliana. In the present study, the effect of exogenous H
2
O
2
on the gravitropic response of primary roots during Arabidopsis seed germination was studied using histology and molecular biology approaches. Appropriate H
2
O
2
treatment not only restrained primary root growth, but also disrupted gravitropism and induced root curvature. Histological staining and molecular analysis demonstrated that exogenous H
2
O
2
correlated with lack of starch-dense amyloplasts in root tip columella cells, which ultimately results in the lack of gravisensing. Detection of calcium ion (Ca
2+
) by a fluorescent probe showed that Ca
2+
distribution changed and intracellular Ca
2+
concentration increased in H
2
O
2
-treated primary root, which was consistent with alterations in auxin distribution and concentration triggered by H
2
O
2
treatment. Furthermore, the normally polar localization of Pin-formed 1 (PIN1) and PIN2 became uniformly distributed on root tip cell membranes after treatment with H
2
O
2
. This leads to speculation that the
IAA
signaling pathway was affected by exogenous H
2
O
2
, causing
asymmetrical
distribution of
IAA
on both sides of the primary root, which would influence the gravitropic response.
...
PMID:Exogenous hydrogen peroxide inhibits primary root gravitropism by regulating auxin distribution during Arabidopsis seed germination. 2977 64
