Katarzyna Marciniak

The Generative Development of Traditional and Self-Completing (Restricted Branching) Cultivars of White Lupin (Lupinus Albus L.), Yellow Lupin (L.Luteus L.) and Narrow-Lafed Lupin (L. Angustifolius L.) Grown under Different Phytotron Conditions

ABSTRACT Increasing the number of flowers and pods set, as well as reducing the intensity of their abortion, is of crucial importance for the yielding of leguminous plants. This study examined the effects of the type of soil used and mineral fertilization applied on the generative development of the traditional and self-completing (restricted branching) cultivars of white lupin (Lupinus albus L.), yellow lupin (L. luteus L.) and narrow-lafed lupin (L. angustifolius L.) cultivated under controlled phytotron conditions. Experiments carried out under such conditions allow for the elimination of variable environmental factors affecting the course of plant ontogenesis in field cultivation, and enable unambiguous interpretation of the biochemical and molecular influence of a selected factor on the physiological process studied. For the first time, the influence of different cultivation factors on generative development of traditional and selfcompleting (restricted branching) cultivars of lupins under phytotrone was examined. The research results presented here indicate that each of the selected lupin cultivars has its own characteristic cultivation conditions that are optimal for its generative development. The largest number of flowers were formed by the traditional cultivars of L. luteus and L. angustifolius, as well as the self-completing (restricted branching) cultivars of L. luteus and L. albus grown in class IIIa soil material. The lowest flower abortion rate was observed in L. albus grown in class V soil material, in L. luteus grown in class IIIa soil material, and in L. angustifolius grown in class IVa soil material. Regardless of the cultivation conditions applied, in all of the lupin cultivars examined the first pods to be set were characterized by the lowest abortion rate. The results obtained allowed for the development of lupin phytotron cultivation models for the purposes of research on generative development control.

Photoperiod and ethylene-dependent expression of gibberellin biosynthesis gene InEKO1 during flower induction of Ipomoea nil

Ent-kaurene oxidase (EKO) catalyze three sequential oxidations in the early steps of gibberellin biosynthesis pathway. In this research, a cDNA sequence of InEKO1 gene in the model short-day plant Ipomoea nil was identified. Our studies revealed that inductive conditions for flowering caused an increase in the transcriptional activity of the examined gene in the cotyledons–the main organs for the perception of the photoperiodic stimulus. In contrast, in the second half of the 16 h long inductive night and after that, a decreased amount of InEKO1 mRNA in the apexes was detected. What is more, ethylene, the key inhibitor of flower induction in I. nil, elevated the InEKO1 expression exclusively in the cotyledons between 10 and 14 h of the inductive night.

Methyl jasmonate-dependent senescence of cotyledons in Ipomoea nil

Jasmonic acid methyl ester (JAMe) has been recently shown to play a crucial role in many physiological processes. In this paper, we focused on cotyledon senescence in Ipomoea nil and revealed that JAMe and darkness are the main factors stimulating the process examined. What is more, we showed that mefenamic acid (a jasmonate biosynthesis inhibitor) reverses the stimulatory effect of darkness on senescence. In plants growing under dark conditions, stimulation of JASMONIC ACID CARBOXYL METHYLTRANSFERASE (InJMT) expression and, consequently, an increase in JAMe content, have been observed. In turn, the level of jasmonic acid (JA) gradually decreased. Moreover, dark-grown seedlings demonstrated a lower PSII functional activity and a reduced chlorophyll content and autofluorescence. All of these data suggest that JAMe is a signal molecule controlling the senescence of cotyledons in I. nil.

De novo Transcriptome Profiling of Flowers, Flower Pedicels and Pods of Lupinus luteus (Yellow Lupine) Reveals Complex Expression Changes during Organ Abscission.

Yellow lupine (Lupinus luteus L., Taper c.), a member of the legume family (Fabaceae L.), has an enormous practical importance. Its excessive flower and pod abscission represents an economic drawback, as proper flower and seed formation and development is crucial for the plants productivity. Generative organ detachment takes place at the basis of the pedicels, within a specialized group of cells collectively known as the abscission zone (AZ). During plant growth these cells become competent to respond to specific signals that trigger separation and lead to the abolition of cell wall adhesion. Little is known about the molecular network controlling the yellow lupine organ abscission. The aim of our study was to establish the divergences and similarities in transcriptional networks in the pods, flowers and flower pedicels abscised or maintained on the plant, and to identify genes playing key roles in generative organ abscission in yellow lupine. Based on de novo transcriptome assembly, we identified 166,473 unigenes representing 219,514 assembled unique transcripts from flowers, flower pedicels and pods undergoing abscission and from control organs. Comparison of the cDNA libraries from dropped and control organs helped in identifying 1,343, 2,933 and 1,491 differentially expressed genes (DEGs) in the flowers, flower pedicels and pods, respectively. In DEG analyses, we focused on genes involved in phytohormonal regulation, cell wall functioning and metabolic pathways. Our results indicate that auxin, ethylene and gibberellins are some of the main factors engaged in generative organ abscission. Identified 28 DEGs common for all library comparisons are involved in cell wall functioning, protein metabolism, water homeostasis and stress response. Interestingly, among the common DEGs we also found an miR169 precursor, which is the first evidence of micro RNA engaged in abscission. A KEGG pathway enrichment analysis revealed that the identified DEGs were predominantly involved in carbohydrate and amino acid metabolism, but some other pathways were also targeted. This study represents the first comprehensive transcriptome-based characterization of organ abscission in L. luteus and provides a valuable data source not only for understanding the abscission signaling pathway in yellow lupine, but also for further research aimed at improving crop yields.

Photoperiodic flower induction in Ipomoea nil is accompanied by decreasing content of gibberellins

The involvement of gibberellins (GAs) in the control of flower induction in the short-day plant Ipomoea nil has been investigated. To clarify the molecular basis of this process, we identified the full-length cDNAs of the InGA20ox3 and InGA2ox1 genes, which encode enzymes responsible for GA biosynthesis and catabolism, respectively. We studied the expression patterns of both genes and determined the tissue and cellular immunolocalisation of gibberellic acid (GA3) in the cotyledons of 5-day-old seedlings growing under inductive and non-inductive photoperiodic conditions. In the second half of the inductive night, which is crucial for flower induction in I. nil, InGA20ox3 expression decreased, whereas InGA2ox1 mRNA accumulated, which indicates that photoperiod regulates the activity of both genes. Furthermore, these changes are correlated with GA3 level. Thus, our results support the thesis that the proper balance between the expression of the InGA20ox3 and InGA2ox1 genes and low GA3 content correlate with photoperiodic flower induction in I. nil.

Gibberellic acid affects the functioning of the flower abscission zone in Lupinus luteus via cooperation with the ethylene precursor independently of abscisic acid

The abscission of plant organs is a phytohormone-controlled process. Our study provides new insight into the involvement of gibberellic acid (GA3) in the functioning of the flower abscission zone (AZ) in yellow lupine (Lupinus luteus L.). Physiological studies demonstrated that GA3 stimulated flower abortion. Additionally, this phytohormone was abundantly presented in the AZ cells of naturally abscised flowers, especially in vascular bundles. Interesting interactions among GA3 and other modulators of flower separation were also investigated. GA3 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. GA3 appears to cooperate with the ET precursor in the regulation of AZ function in L. luteus flowers; however, the presented mechanism is ABA-independent.