Abstract
BackgroundIDA (INFLORESCENCE DEFICIENT IN ABSCISSION)-like signaling peptides and the associated HAE (HAESA)-like family of receptor kinases were originally reported in the model plant Arabidopsis thaliana (Arabidopsis) to be deeply involved in the regulation of abscission. Actually, IDA peptides, as cell-to-cell communication elements, appear to be implicated in many developmental processes that rely on cell separation events, and even in the responses to abiotic stresses. However, the knowledge related to the molecular machinery regulating abscission in economically important crops is scarce. In this work, we determined the conservation and phylogeny of the IDA-like and HAE-like gene families in relevant species of the Solanaceae family and analyzed the expression of these genes in the allopolyploid Nicotiana benthamiana, in order to identify members involved in abscission, stem growth and in the response to drought conditions.ResultsThe phylogenetic relationships among the IDA-like members of the Solanaceae studied, grouped the two pairs of NbenIDA1 and NbenIDA2 protein homeologs with the Arabidopsis prepropeptides related to abscission. Analysis of promoter regions searching for regulatory elements showed that these two pairs of homeologs contained both hormonal and drought response elements, although NbenIDA2A lacked the hormonal regulatory elements. Expression analyses showed that the pair of NbenIDA1 homeologs were upregulated during corolla abscission. NbenIDA1 and NbenIDA2 pairs showed tissue differential expression under water stress conditions, since NbenIDA1 homeologs were highly expressed in stressed leaves while NbenIDA2 homeologs, especially NbenIDA2B, were highly expressed in stressed roots. In non-stressed active growing plants, nodes and internodes were the tissues with the highest expression levels of all members of the IDA-like family and their putative HAE-like receptors.ConclusionOur results suggest that the pair of NbenIDA1 homeologs are involved in the natural process of corolla abscission while both pairs of NbenIDA1 and NbenIDA2 homeologs are implicated in the response to water stress. The data also suggest that IDA peptides may be important during stem growth and development. These results provide additional evidence that the functional module formed by IDA peptides and its receptor kinases, as defined in Arabidopsis, may also be conserved in Solanaceae.
Highlights
IDA (INFLORESCENCE DEFICIENT IN ABSCISSION)-like signaling peptides and the associated HAE (HAESA)-like family of receptor kinases were originally reported in the model plant Arabidopsis thaliana (Arabidopsis) to be deeply involved in the regulation of abscission
The IDA-like gene family in the Solanaceae Table 1 summarizes all IDA-like genes identified in our search in representative species of the genus Nicotiana such as N. sylvestris, N. tomentosiformis, N. tabacum and N. benthamiana in addition to other Solanaceae of agronomic interest such as tomato, potato, eggplant and pepper
IDA-like families of the Nicotiana species N. sylvestris and N. tomentosiformis consisted of 5 members, while in the allopolyploids N. benthamiana and N. tabacum these families are formed by 5 pairs of homeologs, with one exception corresponding to NbenIDA4 whose homeolog pair was not found in the genomic screening
Summary
IDA (INFLORESCENCE DEFICIENT IN ABSCISSION)-like signaling peptides and the associated HAE (HAESA)-like family of receptor kinases were originally reported in the model plant Arabidopsis thaliana (Arabidopsis) to be deeply involved in the regulation of abscission. It is widely accepted that the control of abscission in Arabidopsis requires physical interaction of the hormonal peptide AtIDA, a pair of redundant receptor-like protein kinases, HAESA (HAE) and HAESA- LIKE2 (HSL2), and SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) co-receptors (for a review, see [6]) This interaction activates a signal transduction through a downstream MAP kinase cascade that leads to the expression of multiple abscission-related hydrolytic enzymes such as pectin-methylesterases, polygalacturonases, cellulases, xyloglucan-endotransglycosylase/hydrolases and expansins [7, 8]. The release of this set of enzymes cause the disassembly of the cell wall and the dissolution of the middle lamella, resulting in the detachment of floral organs in Arabidopsis. It has been shown that synthetic IDA peptides were able to induce early floral abscission in Arabidopsis flowers [9]
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