@entity2829 ( @entity2829 ) stem gravitropism involves differential elongation of cells within a highly specialized region, the stem internodal pulvinus. In the present study, we investigated factors that control gravitropic responses in this system. In the graviresponding pulvinus, hexose @entity3363 (D-Glc and D-Fru) accumulated asymmetrically across the pulvinus. This correlated well with an asymmetric increase in acid invertase activity across the pulvinus. Northern analyses revealed asymmetric induction of one @entity2829 acid invertase gene, @entity69571 , consistent with transcriptional regulation by gravistimulation. Several lines of evidence indicated that auxin redistribution, as a result of polar auxin transport, is necessary for gravity-stimulated @entity69571 transcript accumulation and differential cell elongation across the @entity2829 pulvinus. First, the auxin transport inhibitor, @entity51257 , inhibited gravistimulated curvature and @entity69571 transcript accumulation. Second, a transient gradient of free @entity9634 ( @entity6207 ) across the pulvinus was apparent shortly after initiation of gravistimulation. This temporarily free @entity6207 gradient appears to be important for differential cell elongation and @entity69571 transcript accumulation. This is based on the observation that @entity51257 will not inhibit gravitropic responses when applied to pulvinus tissue after the free @entity6207 gradient peak has occurred. Third, @entity6207 alone can stimulate @entity69571 transcript accumulation in non-gravistimulated pulvini. The gravity- and @entity6207 -stimulated increase in @entity69571 transcripts was sensitive to the protein synthesis inhibitor, @entity1880 . Based on these results, a two-phase model describing possible relationships between gravitropic curvature, @entity6207 redistribution, and @entity69571 expression is presented.

Gravity-stimulated changes in auxin and invertase gene expression in XXXX pulvinal cells.

@entity69571 :: ('542324(Tax:4577)', 'Gene') :: ['Ivr2'] @entity51257 :: ('MESH:C002687', 'Chemical') :: ['N-1-naphthylphthalamic acid'] @entity6207 :: ('CHEBI:16411', 'Chemical') :: ['IAA'] @entity3363 :: ('MESH:D002241', 'Chemical') :: ['sugars'] @entity2829 :: ('4577', 'Species') :: ['Maize', 'maize', 'Zea mays'] @entity1880 :: ('MESH:D003513', 'Chemical') :: ['cycloheximide'] @entity9634 :: ('MESH:C030737', 'Chemical') :: ['indole-3-acetic acid']
@entity2829 :: (4577,Species) :: ['maize']
