Ntann12 annexin expression is induced by auxin in tobacco roots

Abstract

Ntann12, encoding a polypeptide homologous to annexins, was found previously to be induced upon infection of tobacco with the bacterium Rhodococcus fascians. In this study, Ntann12 is shown to bind negatively charged phospholipids in a Ca2+-dependent manner. In plants growing in light conditions, Ntann12 is principally expressed in roots and the corresponding protein was mainly immunolocalized in the nucleus. Ntann12 expression was inhibited following plant transfer to darkness and in plants lacking the aerial part. However, an auxin (indole-3-acetic acid) treatment restored the expression of Ntann12 in the root system in dark conditions. Conversely, polar auxin transport inhibitors such as 1-naphthylphthalamic acid (NPA) or 2,3,5-triiodobenzoic acid (TIBA) inhibited Ntann12 expression in light condition. These results indicate that the expression of Ntann12 in the root is linked to the perception of a signal in the aerial part of the plant that is transmitted to the root via polar auxin transport.

Insight into plant annexin function

“…In contrast, following plant transfer to darkness for 48 h, Ntann12 expression was inhibited as well as in plants lacking the aerial part and the corresponding protein was no more detectable. 6 Altogether, these data suggest that light perceived at the leaves surface is the initial signal activating the expression of Ntann12 in the root system of tobacco plantlets. Since auxin has been associated with several light-regulated processes (for a review see ref.…”

“…Besides, light has been reported to affect expression of a number of Arabidopsis and tobacco annexins. 3,6 Finally, annexin expression has been shown to be upregulated during pathogen attack or symbiotic interaction. [7][8][9] The majority of plant annexins has been localized in the cytosol and this localization appear to be dependent on the tissue/ cell type and on the stimulus.…”

“…7,12 and tobacco, 6 but the mechanism of their nuclear import has not been elucidated yet. The dynamic property of plant annexins, as Ca 2+ -dependent proteins that bind to membrane phospholipids, together with their expression patterns, i.e.…”

“…9 Recently, the biochemical properties of Ntann12 were investigated and the data evidenced the capacity of this protein to bind negatively charged phospholipids in a Ca 2+ -dependent manner as well as the modulation by Ca 2+ concentration of the distribution of the native Ntann12 between cytosol and cell membrane fraction. 6 Spatio-temporal analysis revealed that Ntann12 transcript and the corresponding protein are localized within the root system. Besides, pNtann12-GUS transgenic plants indicated that Ntann12 is mainly expressed within the root maturation zone but not in the root cap or in the root elongation zone.…”

“…1) but also in the cytoplasm of root cells. 6 In silico analysis of the 542 bp pNtann12 using PlantPAN 13 indicated the occurrence of nine cis-element sequences possibly implicated in light responses, three GT1 consensus sequences and six GATABOX sequences. To clarify the possible role of Ntann12 in light signaling, we designed experiments at the whole plant level and assessed the effect of light and dark conditions on Ntann12 accumulation in tobacco root system.…”