Search

The abscission of plant organs is a phytohormone-controlled process. Our study provides new insight into the involvement of gibberellic acid (GA 3 ) in the functioning of the flower abscission zone (AZ) in yellow lupine ( Lupinus luteus L.). Physiological studies demonstrated that GA 3 stimulated flower abortion. Additionally, this phytohormone was abundantly presented in the AZ cells of naturally abscised flowers, especially in vascular bundles. Interesting interactions among GA 3 and other modulators of flower separation were also investigated. GA 3 accumulated after treatment with the ethylene (ET) precursor 1-aminocyclopropane-1-carboxylic acid (ACC). Abscisic acid (ABA) treatment did not cause such an effect. Furthermore, the expression of the newly identified LlGA20ox1 and LlGA2ox1 genes encoding 2-oxoglutarate-dependent dioxygenases fluctuated after ACC or ABA treatment which confirmed the existence of regulatory crosstalk. GA 3 appears to cooperate with the ET precursor in the regulation of AZ function in L. luteus flowers; however, the presented mechanism is ABA-independent. [ABSTRACT FROM AUTHOR]

Allene oxide synthase (AOS) encodes the first enzyme in the lipoxygenase pathway, which is responsible for jasmonic acid (JA) formation. In this study we report the molecular cloning and characterization of InAOS from Ipomoea nil. The full-length gene is composed of 1662 bp and encodes for 519 amino acids. The predicted InAOS contains PLN02648 motif, which is evolutionarily conserved and characteristic for functional enzymatic proteins. We have shown that wounding led to a strong stimulation of the examined gene activity in cotyledons and an increase in JA level, which suggest that this compound may be a modulator of stress responses in I. nil. [ABSTRACT FROM AUTHOR]

Drought causes the excessive abscission of flowers in yellow lupine, leading to yield loss and serious economic consequences in agriculture. The structure that determines the time of flower shedding is the abscission zone (AZ). Its functioning depends on the undisturbed auxin movement from the flower to the stem. However, little is known about the mechanism guiding cell–cell adhesion directly in an AZ under water deficit. Therefore, here, we seek a fuller understanding of drought-dependent reactions and check the hypothesis that water limitation in soil disturbs the natural auxin balance within the AZ and, in this way, modifies the cell wall structure, leading to flower separation. Our strategy combined microscopic, biochemical, and chromatography approaches. We show that drought affects indole-3-acetic acid (IAA) distribution and evokes cellular changes, indicating AZ activation and flower abortion. Drought action was manifested by the accumulation of proline in the AZ. Moreover, cell wall-related modifications in response to drought are associated with reorganization of methylated homogalacturonans (HG) in the AZ, and upregulation of pectin methylesterase (PME) and polygalacturonase (PG)—enzymes responsible for pectin remodeling. Another symptom of stress action is the accumulation of hemicelluloses. Our data provide new insights into cell wall remodeling events during drought-induced flower abscission, which is relevant to control plant production. [ABSTRACT FROM AUTHOR]

Plant senescence is a highly regulated process that allows nutrients to be mobilized from dying tissues to other organs. Despite that senescence has been extensively studied in leaves, the senescence of ephemeral organs located underground is still poorly understood, especially in the context of phytohormone engagement. The present study focused on filling this knowledge gap by examining the roles of abscisic acid (ABA) and jasmonate in the regulation of senescence of fine, absorptive roots and leaves of Populus trichocarpa. Immunohistochemical (IHC), chromatographic, and molecular methods were utilized to achieve this objective. A transcriptomic analysis identified significant changes in gene expression that were associated with the metabolism and signal transduction of phytohormones, especially ABA and jasmonate. The increased level of these phytohormones during senescence was detected in both organs and was confirmed by IHC. Based on the obtained data, we suggest that phytohormonal regulation of senescence in roots and leaves is organ-specific. We have shown that the regulation of ABA and JA metabolism is tightly regulated during senescence processes in both leaves and roots. The results were discussed with respect to the role of ABA in cold tolerance and the role of JA in resistance to pathogens. [ABSTRACT FROM AUTHOR]

• Drought stress decreased water content directly in nodules and caused degradation of symbiosome. • Hormonal changes evoked by water deficit are reflected by the affection of ET and ABA biosynthesis pathway. • The stress factor negatively regulated the expression of LlBOP and LlLbl genes responsible for the proper functioning of the nodules. • We provide several potential molecular and hormonal markers related to the response on soil drought. The ability of symbiosis with Rhizobium bacteria is an extremely important trait of Lupinus luteus L. Its cultivation increases soil fertility and reduces the necessity of using chemical fertilizers, thus makes lupine an excellent proecological and agronomical species. Nevertheless, nodule functioning associated with nitrogen fixation can be strongly affected by soil drought. On the face of changing climatic conditions, the emphasis should be given to get the knowledge concerning the phytohormonal and molecular markers of early response on water deficit in soil. In this paper, we have shown that soil drought stress, by causing water loss in nodules and affecting their structure, evokes degradation of symbiosome and leads to hormonal and molecular changes. The stress factor modulated abscisic acid (ABA) and ethylene (ET) biosynthesis pathways. It was reflected by increased expression of LlZEP (ZEAXANTHIN EPOXIDASE) involved in ABA biosynthesis and strong accumulation of this phytohormone. At the same time, the mRNA of synthase (LlACS) and oxidase (LlACO) of 1-aminocyclopropane-1-carboxylic acid (ACC) were elevated, while ACC accumulated significantly. Moreover, drought stress negatively influenced the expression of LlBOP (BLADE-ON-PETIOLE) and LlLbI (LEGHEMOGLOBIN), previously pointed out as regulators of nodule functioning. Simultaneously the iron and nitrogen content drastically decreased in the stressed nodules. Presented novel information describing phytohormonal changes during drought stress directly in the nodules can help to elucidate the hormonal and molecular mechanisms that control plant response to water loss. [ABSTRACT FROM AUTHOR]