Abstract
Abscission is a natural process that occurs to facilitate shedding of no longer needed organs, but on the other hand, can be triggered by certain environmental conditions, e.g. biotic or abiotic stresses. Regardless of the stimuli, organ shedding takes place specifically at the abscission zone (AZ). A signaling pathway that controls this process in Arabidopsis thaliana from ligand to receptors has been proposed. However, knowledge concerning the influence of plant hormones on these molecular elements still remains enigmatic. Excessive and premature flower abscission in the crop species Lupinus luteus L. is a process of substantial interest to the agricultural industry, as it can affect yield. Our strategy combined molecular studies, comprehensive ultrastructural and histological analysis, as well as exogenous hormone treatment to describe the contribution of the Lupinus IDA-like gene in flower abscission. In the AZ of the naturally abscised flowers, the differentiation of morphologically distinct cells characterized by progressive degradation processes was accompanied by LlIDL mRNA accumulation. A similar effect was observed following early steps of AZ activation and after abscisic acid or ethylene treatments. These phytohormones, previously pointed out as key stimulators of flower separation, altered the temporal expression pattern of LlIDL. Exogenous EPIP peptide synthesized on the basis of LlIDL sequence, significantly increased flower abortion rate, which indicates that this motif governs protein activity. In conclusion, our data provide new evidence for LlIDA involvement in both the early and late events of flower abscission supported by detailed spatiotemporal characterization of AZ cell structure and ultrastructure.
Highlights
The shedding of various plant organs is a part of a natural developmental program
IDA from A. thaliana has been postulated to be regulated in an ET-independent manner (Butenko et al 2003). It seems that the elements of the genetic pathway that leads to organ separation are similar
We present a report of identified LlIDL gene in L. luteus
Summary
The shedding of various plant organs is a part of a natural developmental program. This phenomenon is often associated with reproduction, senescence, defense and response on stress factors. Plant Growth Regulation (2018) 85:91–100 established that flowers and fruits abscission occurs after activation of a functionally specialized group of cells called abscission zone (AZ) This zone is located usually at their bases (Estornell et al 2013). It was experimentally established that IDA-HAE/HSL2 complex induces a MITOGEN-ACTIVATED PROTEIN KINASE (MAP) cascade within the cytoplasm of AZ cells This pathway suppresses KNOTTED-LIKE HOMEOBOXlike (KNOX-like) transcription factor—KNAT1, which in turn allows KNAT2 and KNAT6 to induce organ abscission (Cho et al 2008; Shi et al 2011). It seems that the elements of the genetic pathway that leads to organ separation are similar Their activity is controlled in particular plant species by various plant hormones and other factors. Our paper is a new evidence on the phytohormonedependent regulation of LlIDL gene during flower separation processes in yellow lupine at the level of AZ cells
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