Cytokinin-Induced Parthenocarpic Fruit Development in Tomato Is Partly Dependent on Enhanced Gibberellin and Auxin Biosynthesis

Fruit set of plants largely depends on the biosynthesis and crosstalk of phytohormones. To date the role of cytokinins (CKs) in the fruit development is less understood. Here, we showed that parthenocarpic fruit could be induced by 1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU, an active CK) in tomato ( Solanum lycopersicum cv. Micro-Tom). The fresh weight of CPPU-induced parthenocarpic fruits was comparable with that induced by GA₃. Importantly, CPPU-induced parthenocarpy was found to be compromised by simultaneous application of paclobutrazol (a GA biosynthesis inhibitor), and this effect could be restored by exogenous GA₃. Like pollination, CPPU-induced fruit showed enhanced accumulation of GA₁₊₃ and indole-3-acetic (IAA), which were accompanied by elevated expression of GA biosynthesis genes like SlGPS, SlGA20ox1, SlGA20ox2 and SlGA3ox1, and IAA biosynthesis gene ToFZY. Elevated GAs level in CPPU-induced fruits was also associated with down-regulation of GA inactivation genes, namely SlGA2ox1,2,3,4,5 in comparison with untreated control. These results suggested that CKs may induce parthenocarpy in tomato partially through modulation of GA and IAA metabolisms.     

Effect of Gibberellin and Auxin on Parthenocarpic Fruit Growth Induction in the cv Micro-Tom of Tomato

The effect of applied gibberellin (GA) and auxin on fruit-set and growth has been investigated in tomato (Solanum lycopersicum L.) cv Micro-Tom. It was found that to prevent competition between developing fruits only one fruit per truss should be left on the plant. Unpollinated ovaries responded to GA₃ and to different auxins [indol-3-acetic acid, naphthaleneacetic acid, and 2,4-dichlorophenoxyacetic acid (2,4-D)], 2,4-D being the most efficient. GA₃- and 2,4-D-induced fruits had different internal morphology, with poor locular tissue development in the case of GA, and pseudoembryos development in the case of 2,4-D. Also, GA₃ produced larger cells in the internal region of the mesocarp (IM) associated with higher mean C values, whereas 2,4-D produced more cell layers in the pericarp than pollinated fruits. The smaller size of GA₃- compared with 2,4-D-induced fruits was due to them having fewer cells, only partially compensated by the larger size of IM cells. Simultaneous application of GA₃ and 2,4-D produced parthenocarpic fruits similar to pollinated fruits, but for the absence of seeds, suggesting that both kinds of hormones are involved in the induction of fruit development upon pollination. It is concluded that Micro-Tom constitutes a convenient model system, compared to tall cultivars, to investigate the hormonal regulation of fruit development in tomato.     

Effects of Brassin-Complex on Auxin and Gibberellin Mediated Events in the Morphogenesis of the Etiolated Bean Hypocotyl

The excised, hooked bean hypocotyl was the system used to determine wheiher the ‘auxin- and gibberellin like’ effect of the lipoidal pollen extract, Brass in-complex (Br), were mediated through, or independent of, auxin and gibberellin. The morphogenetic events of hook opening and hypocotyl elongation in this system are regulated by auxin and gibberellin, respectively. Brassin complex, like IAA, elicited a book closure in (he dark and retarded its opening in red light. This effect was synergized by T1BA, IAA and the presence of the auxin-producing organs, the epicotyl and cotyledons. Br-elicited hook closure was inhibited by the antiauxin. PCIB. Both GA₃ and Br totally reversed the light inhibition of hypocotyl elongation. The GA₃-effect, but nol the Br elicited elongation, was overcome by Ancymidol. Hypocotyl elongation was partially inhibited by TIBA and PCIB. suggesting a possible auxin involvement also in this effect of Br. Br may elicit its growth responses through an effect on endogenous auxin levels, In this way it is different from other lipoidat growth regulators, such as the oleanimins which require the presence of exogenous growth regulators for activity.     

Deep Sequencing of the Scutellaria baicalensis Georgi Transcriptome Reveals Flavonoid Biosynthetic Profiling and Organ-Specific Gene Expression

Scutellaria baicalensis Georgi has long been used in traditional medicine to treat various such widely varying diseases and has been listed in the Chinese Pharmacopeia, the Japanese Pharmacopeia, the Korean Pharmacopoeia and the European Pharmacopoeia. Flavonoids, especially wogonin, wogonoside, baicalin, and baicalein, are its main functional ingredients with various pharmacological activities. Although pharmaological studies for these flavonoid components have been well conducted, the molecular mechanism of their biosynthesis remains unclear in S. baicalensis. In this study, Illumina/Solexa deep sequencing generated more than 91 million paired-end reads and 49,507 unigenes from S. baicalensis roots, stems, leaves and flowers. More than 70% unigenes were annotated in at least one of the five public databases and 13,627 unigenes were assigned to 3,810 KEGG genes involved in 579 different pathways. 54 unigenes that encode 12 key enzymes involved in the pathway of flavonoid biosynthesis were discovered. One baicalinase and three baicalein 7-O-glucuronosyltransferases genes potentially involved in the transformation between baicalin/wogonoside and baicalein/wogonin were identified. Four candidate 6-hydroxylase genes for the formation of baicalin/baicalein and one candidate 8-O-methyltransferase gene for the biosynthesis of wogonoside/wogonin were also recognized. Our results further support the conclusion that, in S. baicalensis, 3,5,7-trihydroxyflavone was the precursor of the four above compounds. Then, the differential expression models and simple sequence repeats associated with these genes were carefully analyzed. All of these results not only enrich the gene resource but also benefit research into the molecular genetics and functional genomics in S. baicalensis.     

Arginase,Arginine Decarboxylase,Ornithine Decarboxylase,and Polyamines in Tomato Ovaries (Changes in Unpollinated Ovaries and Parthenocarpic Fruits Induced by Auxin or Gibberellin)

Arginase (EC 3.5.3.1) activity has been found in the ovaries and Young fruits of tomato (Lycopersicon esculentum Mill. cv Rutgers).Changes in arginase, arginine decarboxylase (EC 4.1.1.19), and ornithine decarboxylase activity (EC 4.1.1.17) and levels of free and conjugated putrescine, spermidine, and spermine were determined in unpollinated ovaries and in parthenocarpic fruits during the early stages of development induced by 2,4-dichlorophenoxyacetic acid (2,4-D) or gibberellic acid (GA3). Levels of arginase, free spermine, and conjugates of the three polyamines were constant in unpollinated ovaries and characteristic of a presenescent step. A marked decrease in arginase activity, free spermine, and polyamine conjugates was associated with the initiation of fruit growth due to cell division, and when cell expansion was initiated, the absence of arginase indicated a redirection of nitrogen metabolism to the synthesis of arginine. A transient increase in arginine decarboxylase and ornithine decarboxylase was also observed in 2,4-D-induced fruits. In general, 2,4-D treatments produced faster changes than GA3, and without treatment, unpollinated ovaries developed only slightly and senescence was hardly visible. Sensitivity to 2,4-D and GA3 treatment remained for at least 2 weeks postanthesis.     

Application of a Rapid and Sensitive Method for Hormonal and Vitamin E Profiling Reveals Crucial Regulatory Mechanisms in Flower Senescence and Fruit Ripening

Knowledge of ripeness and regulation of postharvest processes is an important tool to prevent loss of commercial value in both fruit and cut flower markets. The joint analysis of hormones and vitamin E levels can reveal complex interactions between hormones and oxidative stress as key regulators of postharvest processes. Profiling of both groups of metabolic compounds was performed during the ripening of non-climacteric fruits (red raspberry, Rubus idaeus L.) and senescence of ethylene-insensitive flowers (Dutch Iris, Iris x hollandica L.). After an initial extraction of the sample, without further purification steps, the hormonal profile was analyzed by UPLC-MS/MS and vitamin E levels were measured by HPLC. This methodological approach was very fast and had enough sensitivity for the analysis of small samples. Raspberry fruit maturation was characterized by a decline of cytokinin levels [zeatin, zeatin riboside, 2-isopentenyl adenine, and isopentenyl adenosine (Z, ZR, 2-iP, and IPA, respectively)] and gibberellins (GA₁ in particular). Exogenous application of ABA prevented δ-tocopherol loss during fruit ripening. Iris floral senescence was also under strict hormonal control, also mediated by cytokinins and gibberellins. Z, ZR, 2-iP, GA₉, and GA₂₄ levels decreased in inner tepals, whereas the level of IPA decreased in style-merged-to-stigma tissues, thus suggesting tissue-specific roles for different hormones. α-Tocopherol levels decreased during senescence of inner tepals, hence suggesting enhanced oxidative stress. In conclusion, the rapid and sensitive hormonal and vitamin E profiling presented here can help in understanding the key physiological processes underlying fruit ripening and floral senescence.     

Comparative Transcriptomic Analysis Reveals the Regulatory Mechanism of Terpene Trilactones Improvement by Exogenous Methyl Jasmonate in Ginkgo biloba

Introduction

 Terpene trilactones (TTLs) are one of the main active ingredients of Ginkgo biloba. Owing to TTL’s unique chemical structure, it is difficult to increase TTL content through chemical and biological methods. Studying its regulatory mechanism is important in the G. biloba industry.

Results

The effect of exogenous methyl jasmonate (MeJA) on the physiological and molecular mechanism of TTL biosynthesis was studied. These results showed that MeJA treatment could improve the TTL contents, soluble sugar, starch, soluble protein, endogenous hormones (ZT, GA3, IAA, and ABA), antioxidant enzymes (catalase, peroxidase, and superoxide dismutase), and the efficiency of photosynthesis in G. biloba leaves. A total of 100 differentially expressed genes (DEGs) were identified between the control group and MeJA treatment through RNA-seq analysis. The results indicated that exogenous MeJA treatment upregulated the expression levels of the following genes: BMY (beta-amylase) in the starch and sucrose metabolic pathway; PEX7 (peroxin-7) in the peroxisome pathway; psbA (photosystem II reaction center D1 protein), psbC (photosystem II CP43 chlorophyll apoprotein), psaA (photosystem I P700 chlorophyll a apoprotein A1), and petF (photosynthetic electron transport ferredoxin) in the photosynthesis pathway; and CYP450 (Gb-16765) (cytochromeP450).

Conclusions

Exogenous MeJA treatment can promote physiological indexes (photosynthetic efficiency, starch, sucrose, antioxidant enzyme activities, etc.) and then regulating differential genes, thus controlling the synthesis of TTLs.