Floral Tissues Research Articles

Botrytis cinerea as the causal agent of grey mould on floral tissue of mango in Japan

In March 2016, grey mould disease was observed on mango (Mangifera indica) in Okinawa Prefecture, Japan. During the flowering period, the disease caused a brown coloration of the petals and peduncles accompanied by white aerial mycelium. As the disease symptoms progressed, the rot of panicle parts was accompanied by grey mould, resulting in fruit set failure. A fungus was isolated from the discoloured inflorescence into pure culture. Based on morphology and analyses of glyceraldehyde-3-phosphate dehydrogenase (g3pdh), heat-shock protein 60 (hsp60) and DNA-dependent RNA polymerase subunit II (rpb2) DNA sequences the fungus was identified as Botrytis cinerea. In an inoculation test, the isolate reproduced the symptoms observed on mango petals and peduncles and was reisolated from the flowers. This is the first report of B. cinerea as the causal agent of grey mould (haiirokabi-byo in Japanese) on floral tissue of mango in Japan.

Preferential freezing avoidance localised in anthers and embryo sacs in wintering Daphne kamtschatica var. jezoensis flower buds visualised by magnetic resonance imaging.

To explore diversity in cold hardiness mechanisms, high resolution magnetic resonance imaging (MRI) was used to visualise freezing behaviours in wintering Daphne kamtschatica var. jezoensis flower buds, which have naked florets and no bud scales. MRI images showed that anthers remained stably supercooled to the range from -14 to -21°C or lower while most other tissues froze by -7°C. Freezing of some anthers detected in MRI images between -14 and -21°C corresponded with numerous low temperature exotherms and also with the 'all-or-nothing' type of anther injuries. In ovules/pistils, only embryo sacs remained supercooled at -7°C or lower, but slowly dehydrated during further cooling. Cryomicroscopic observation revealed ice formation in the cavities of calyx tubes and pistils but detected no ice in embryo sacs or in anthers. The distribution of ice nucleation activity in floral tissues corroborated the tissue freezing behaviours. Filaments likely work as the ice blocking barrier that prevents ice intrusion from extracellularly frozen calyx tubes to connecting unfrozen anthers. Unique freezing behaviours were demonstrated in Daphne flower buds: preferential freezing avoidance in male and female gametophytes and their surrounding tissues (by stable supercooling in anthers and by supercooling with slow dehydration in embryo sacs) while the remaining tissues tolerate extracellular freezing.

Observation of unexpected neo like-fruit development from Cakile maritima calli

Parthenocarpy, the ability of some plants to undergo fruit growth in absence of fertilization, is an important question of basic science and the subject of much interest due to its possible agricultural benefits. In the context of our cellular biology studies on a halophyte of interest, Cakile maritima, we generated calli, pluripotent cell masses, that unexpectedly allowed the appearance of parthenocarpic fruits without any floral tissues. These observations raise the hope to develop an in vitro model to study parthenocarpic fruit development.

Genome-Wide Identification and Expression Analysis of LBD Transcription Factor Genes in Passion Fruit (Passiflora edulis).

The lateral organ boundary domain (LBD) gene is a plant-specific transcription factor that plays a crucial role in plant growth and development, including the development of lateral vegetative organs such as leaf and root development, as well as floral organs such as sepal, petal, and pollen development. Passion fruit is a tropical fruit with important agricultural, economic and ornamental value. However, there is no systematic research report available on the LBD gene family of passion fruit. In this study, a genome-wide analysis of passion fruit LBD genes identified 33 PeLBDs that were unevenly distributed across nine chromosomes. According to phylogenetic and gene structure analysis, PeLBDs were divided into two categories: Class I (27) and Class II (6). Homologous protein modeling results showed that the gene members of the two subfamilies were structurally and functionally similar. Cis-acting element and target gene prediction analysis suggested that PeLBDs might participate in various biological processes by regulating diverse target genes involved in growth and development, metabolism, hormones and stress response. Collinearity analysis indicated that the expansion of the PeLBD gene family likely took place mainly by segmental duplication, and some duplicated gene pairs such as PeLBD13/15 might show functional redundancy, while most duplicated gene pairs such as PeLBD8/12 showed different expression profiles indicating their functional diversification. After filtering low expressed genes, all Class Id PeLBDs were more highly expressed during pollen development. At the same, all Class Ic and many other PeLBDs were relatively highly expressed during ovule development, similar with their homologous LBD genes in Arabidopsis, indicating their potential regulatory roles in reproductive tissue development in passion fruit. PeLBDs that were highly expressed in floral tissues were also expressed at a higher level in tendrils with some differences, indicating the close relationships of tendrils to floral tissues. Some genes such as PeLBD23/25 might be simultaneously related to floral development and leaf early formation in passion fruit, while other PeLBDs showed a strong tissue-specific expression. For example, PeLBD17/27/29 were specifically expressed in floral tissues, while PeLBD11 were only highly expressed in fruit, suggesting their specific function in the development of certain tissues. A qRT-PCR was conducted to verify the expression levels of six PeLBDs in different tissues. Our analysis provides a basis for the functional analysis of LBD genes and new insights into their regulatory roles in floral and vegetative tissue development.

Identification and Characterization of Two Regiospecific Tricetin UDP-Dependent Glycosyltransferases from Pomegranate (Punica granatum L.).

Tricetin (5,7,3′,4′,5′-pentahydroxyflavone) is a dietary flavone from flowers of Myrtales plants with demonstrated functions in promoting human health. By contrast, the bioactivity of its glucosylated derivative tricetin 4′-O-glucoside has not been extensively explored. We conducted metabolite profiling analysis of pomegranate (a Myrtales plant) floral tissues and revealed that tricetin and tricetin 4′-O-glucoside accumulate in anthers, but not petals. In addition, the comparative analysis of anther and petal transcriptomes identified 10 UGTs that are more highly expressed in anthers than petals. Of the 10 UGTs, PgUGT76Z1 and PgUGT73AL1 glucosylated specifically at the 4′-O position of tricetin to form tricetin 4′-O-glucoside. The phylogenetic analysis indicated that PgUGT76Z1 and PgUGT73AL1 belong to different plant UGT groups, suggesting a convergent evolution of these tricetin UGTs. Overall, identification and characterization of PgUGT76Z1 and PgUGT73AL1 not only provides evolutionary insights into tricetin glucosylation, but also offers an opportunity to produce tricetin 4′-O-glucoside in large quantities through microbial biotransformation or plant metabolic engineering, thus facilitating the investigation of tricetin 4′-O-glucoside bioactivities.

Transcriptome analyses shed light on floral organ morphogenesis and bract color formation in Bougainvillea

BackgroundBougainvillea is a popular ornamental plant with brilliant color and long flowering periods. It is widely distributed in the tropics and subtropics. The primary ornamental part of the plant is its colorful and unusual bracts, rich in the stable pigment betalain. The developmental mechanism of the bracts is not clear, and the pathway of betalain biosynthesis is well characterized in Bougainvillea.ResultsAt the whole-genome level, we found 23,469 protein-coding genes by assembling the RNA-Seq and Iso-Seq data of floral and leaf tissues. Genome evolution analysis revealed that Bougainvillea is related to spinach; the two diverged approximately 52.7 million years ago (MYA). Transcriptome analysis of floral organs revealed that flower development of Bougainvillea was regulated by the ABCE flower development genes; A-class, B-class, and E-class genes exhibited high expression levels in bracts. Eight key genes of the betalain biosynthetic pathway were identified by homologous alignment, all of which were upregulated concurrently with bract development and betalain accumulation during the bract initiation stage of development. We found 47 genes specifically expressed in stamens, including seven highly expressed genes belonging to the pentose and glucuronate interconversion pathways. BgSEP2b, BgSWEET11, and BgRD22 are hub genes and interacted with many transcription factors and genes in the carpel co-expression network.ConclusionsWe assembled protein-coding genes of Bougainvilea, identified the floral development genes, and constructed the gene co-expression network of petal, stamens, and carpel. Our results provide fundamental information about the mechanism of flower development and pigment accumulation in Bougainvillea, and will facilitate breeding of cultivars with high ornamental value.

Comparing the Fungicide Sensitivity of Sclerotinia sclerotiorum Using Mycelial Growth and Ascospore Germination Assays.

The infection of the floral tissues of snap bean and other crops by Sclerotinia sclerotiorum, the causative agent of white mold, is by ascospores. Irrespective of the fungicide mode of action being evaluated, invitro fungicide sensitivity tests are conducted almost exclusively using mycelial growth assays. This is likely because of difficulties and time involved in sclerotial conditioning required to produce apothecia and ascospores. The objective of this research was to compare estimates of fungicide sensitivity between mycelial growth and ascospore germination assays for S. sclerotiorum. Sensitivity assays were conducted using serial doses of three fungicides commonly used to control white mold: boscalid, fluazinam, and thiophanate-methyl. A total of 27 isolates were evaluated in replicated trials conducted for each fungicide and assay type. The effective concentration to reduce mycelial growth or ascospore germination by 50% (EC50) was estimated for each isolate, fungicide, and assay type. The median EC50 values obtained from ascospore germination assays were 52.7, 10.0, and 2.7 times higher than those estimated from the mycelial growth for boscalid, fluazinam, and thiophanate-methyl, respectively. No significant correlation was found between EC50 values estimated by the two methods. These findings highlight differences that may be important in evaluating the sensitivity of S. sclerotiorum given the fungicide mode of action and how they will be used in the field.

Flowers prepare thyselves: leaf and root herbivores induce specific changes in floral phytochemistry with consequences for plant interactions with florivores.

Summary The phenotypic plasticity of flowering plants in response to herbivore damage to vegetative tissues can affect plant interactions with flower‐feeding organisms. Such induced systemic responses are probably regulated by defence‐related phytohormones that signal flowers to alter secondary chemistry that affects resistance to florivores. Current knowledge on the effects of damage to vegetative tissues on plant interactions with florivores and the underlying mechanisms is limited.We compared the preference and performance of two florivores on flowering Brassica nigra plants damaged by one of three herbivores feeding from roots or leaves. To investigate the underlying mechanisms, we quantified expression patterns of marker genes for defence‐related phytohormonal pathways, and concentrations of phytohormones and glucosinolates in buds and flowers.Florivores displayed contrasting preferences for plants damaged by herbivores feeding on roots and leaves. Chewing florivores performed better on plants damaged by folivores, but worse on plants damaged by the root herbivore. Chewing root and foliar herbivory led to specific induced changes in the phytohormone profile of buds and flowers. This resulted in increased glucosinolate concentrations for leaf‐damaged plants, and decreased glucosinolate concentrations for root‐damaged plants.The outcome of herbivore–herbivore interactions spanning from vegetative tissues to floral tissues is unique for the inducing root/leaf herbivore and receiving florivore combination.

Genome-Wide Identification and Analysis of Cell Cycle Genes in Birch

Research Highlights: This study identified the cell cycle genes in birch that likely play important roles during the plant’s growth and development. This analysis provides a basis for understanding the regulatory mechanism of various cell cycles in Betula pendula Roth. Background and Objectives: The cell cycle factors not only influence cell cycles progression together, but also regulate accretion, division, and differentiation of cells, and then regulate growth and development of the plant. In this study, we identified the putative cell cycle genes in the B. pendula genome, based on the annotated cell cycle genes in Arabidopsis thaliana (L.) Heynh. It can be used as a basis for further functional research. Materials and Methods: RNA-seq technology was used to determine the transcription abundance of all cell cycle genes in xylem, roots, leaves, and floral tissues. Results: We identified 59 cell cycle gene models in the genome of B. pendula, with 17 highly expression genes among them. These genes were BpCDKA.1, BpCDKB1.1, BpCDKB2.1, BpCKS1.2, BpCYCB1.1, BpCYCB1.2, BpCYCB2.1, BpCYCD3.1, BpCYCD3.5, BpDEL1, BpDpa2, BpE2Fa, BpE2Fb, BpKRP1, BpKRP2, BpRb1, and BpWEE1. Conclusions: By combining phylogenetic analysis and tissue-specific expression data, we identified 17 core cell cycle genes in the Betulapendula genome.

Weight Gain of Spodoptera frugiperda Larvae (Lepidoptera: Noctuidae) on Leaf and Floral Tissues of Silphium integrifolium (Asterales: Asteraceae) Differs by Plant Genotype.

Silflower (Silphium integrifolium (Michaux)) is a native North American relative of sunflower that is undergoing domestication as a perennial oilseed crop. As silflower incurs pest damage from multiple insect species, it is necessary to screen genotypes for their effect on insect performance such that more pest tolerant/resistant accessions can be incorporated into future silflower breeding programs. We present a bioassay protocol for silflower using the generalist herbivore fall armyworm (Spodoptera frugiperda (J. E. Smith)). In this study, fall armyworm larvae were placed on leaf and flower tissue from eleven silflower genotypes, one cup plant (Silphium perfoliatum (L.) (Asterales: Asteraceae)) genotype, and an inbred sunflower line (Helianthus annuus (L.) (Asterales: Asteraceae), HA89). Caterpillar weight gained during a 4-d feeding period significantly differed on leaf and floral tissue from different silflower genotypes, between the Silphium species (silflower and cup plant), and between Silphium genotypes and annual sunflower. Two wild silflower genotypes produced lower larval weight gain on both the floral and leaf tissue than all other genotypes, suggesting these genotypes have either lower nutrition or greater resistance to fall armyworm. However, nonsignificant correlations between larval growth on floral versus leaf tissue across all plant species tested and among all silflower accessions suggest insect performances on these tissue types in silflower are independent. Along with identifying germplasm of interest for silflower breeding programs, we established an easily replicable bioassay protocol using fall armyworm on silflower floral and leaf tissues.

Conteúdo de compostos fenólicos em mel monofloral de aroeira e no tecido do nectário floral

Abstract The objective of this work was to quantify the content of total phenolic compounds in monofloral honey from aroeira (Astronium urundeuva) trees and to verify, through histochemical tests, if these compounds are present in the floral tissues. The apiary, with Apis mellifera bees, was installed among aroeira trees in the semiarid region of the state of Minas Gerais, Brazil. From the anatomy of the flowers and of the inflorescence rachis, an ornamented epidermis, tector and glandular trichomes, idioblasts, and a developed secretory system were observed. Aroeira honey has an average phenolic content of 142.5±22.6 mg 100 g-1, a value considered very high when compared with those of other monofloral honeys from Brazil and around the world. Histochemical tests detected the presence of phenolic substances in the idioblasts and secretory ducts associated with the phloem in the floral tissues, especially in the nectar parenchyma, epidermis, and glandular trichomes. Phenolic compounds are present in the floral tissue of both floral morphs, mainly in the nectary where honeybees collect nectar. The obtained results are the first, in the literature, indicative that the phenolic compounds produced by aroeira trees are transferred through the nectar to the honey. This study contributes to the establishment of quality standards for monofloral aroeira honey and to the identification of its botanical origin.

Ammonium and nitrate impact petal color traits and amino acid profiles differently in <i>Petunia</i>

Nitrogen (N) is vital for ornamental plants to fulfill fundamental cellular functions. Effects of inorganic N including nitrate and ammonium on ornamental traits at the biochemical level are less reported. Given that the continuously increased concentration of CO₂ in atmosphere has greater negative effects on nitrate reduction than ammonium utilization in C₃ plants, it is vital for us to dissect various effects of different inorganic N forms on flower development, which will lead to a better understanding of the metabolic regulation of ornamental traits. In this study, <italic>Petunia x hybrida</italic> cv 'Mitchell Diploid' (MD) plants at 6~8-leaf stage were treated hydroponically with the same and regular amount of inorganic N for one month but in three different forms, 1mM NH₄NO₃ as the control (NH₄NO₃), 2mM NH₄Cl alone (NH₄-N) and 2mM NaNO₃ alone (NO₃-N). Results indicated that relative to the control, effects of NH₄-N and NO₃-N treatment alone on plant growth, N utilization and distribution, petal color traits and petal amino acid profiles were different by varying degrees. We have confirmed that NH₄-N could specifically increase ¹⁵N distribution to floral tissues, change the amino acid profiles in petals which in turn bring changes to petal colors. Results with four commercially available petunia cultivars with different flower colors also validated our findings. This study has been designed to specifically investigate effects of ammonium or nitrate as the sole source of inorganic N on the developmental and chemical features of floral tissues in <italic>Petunia</italic>.

Transcriptomic Analysis of Sex-Associated DEGs in Female and Male Flowers of Kiwifruit (Actinidia deliciosa [A. Chev] C. F. Liang &amp; A. R. Ferguson)

Kiwifruit (Actinidia deliciosa [A. Chev.], C.V. Liang &amp; A. R. Ferguson, 1984) is a perennial plant, with morphologically hermaphroditic and functionally dioecious flowers. Fruits of this species are berries of great commercial and nutritional importance. Nevertheless, few studies have analyzed the molecular mechanisms involved in sexual differentiation in this species. To determine these mechanisms, we performed RNA-seq in floral tissue at stage 60 on the BBCH scale in cultivar ‘Hayward’ (H, female) and a seedling from ‘Green Light’ × ‘Tomuri’ (G × T, male). From these analyses, we obtained expression profiles of 24,888 (H) and 27,027 (G × T) genes, of which 6413 showed differential transcript abundance. Genetic ontology (GO) and KEGG analysis revealed activation of pathways associated with the translation of hormonal signals, plant-pathogen interaction, metabolism of hormones, sugars, and nucleotides. The analysis of the protein-protein interaction network showed that the genes ERL1, AG, AGL8, LFY, WUS, AP2, WRKY, and CO, are crucial elements in the regulation of the hormonal response for the formation and development of anatomical reproductive structures and gametophytes. On the other hand, genes encoding four Putative S-adenosyl-L-methionine-dependent methyltransferases (Achn201401, Achn281971, Achn047771 and Achn231981) were identified, which were up-regulated mainly in the male flowers. Moreover, the expression profiles of 15 selected genes through RT-qPCR were consistent with the results of RNA-seq. Finally, this work provides gene expression-based interactions between transcription factors and effector genes from hormonal signaling pathways, development of floral organs, biological and metabolic processes or even epigenetic mechanisms which could be involved in the kiwi sex-determination. Thus, in order to decode the nature of these interactions, it could be helpful to propose new models of flower development and sex determination in the Actinidia genus.

Evaluating Postharvest Organic Nitrogen Fertilizer Applications in Early Fruiting Northern Highbush Blueberry

Bloom to fruit maturity is a period of rapid growth and nitrogen (N) uptake in northern highbush blueberry (Vaccinium corymbosum L.). Sufficient plant-available N is critical during this time, and growers often accomplish this through fertilizer applications from bloom through fruit development. For organic production in northern climates like Washington State, postharvest applications of N fertilizer are not recommended for northern highbush blueberry because they may stimulate excessive vegetative growth, reduce floral bud set, and increase the risk of winter injury through delayed acclimation. However, early fruiting cultivars with the potential for an extended growing season after harvest may benefit from postharvest N applications because the additional N may promote shoot and root growth that could support fruit production in future years while still allowing plants to form floral buds and acclimate to winter temperatures. The objective of this study was to evaluate the potential impacts of postharvest organic N fertilizer applications on ‘Duke’, an early fruiting northern highbush blueberry cultivar. Specific objectives were to determine the effects of postharvest organic N fertilizer application on plant growth, yield, floral bud set, fruit quality, cold hardiness, tissue macronutrient concentrations, and select soil properties. Four treatments varying in the timing of N application were evaluated in a commercial ‘Duke’ field in eastern Washington using a single fertilizer rate of 130 kg⋅ha−1 N from 2018 to 2020. The organic fertilizer N source was a liquid fertilizer derived from digested plant materials. The experimental design was a randomized complete block design with four replications and treatments included the following: control (100% of N applied preharvest); 80/20 (80% preharvest, 20% postharvest); 70/30 (70% preharvest, 30% postharvest); and 60/40 (60% preharvest, 40% postharvest). Although the year influenced measured variables, including yield, floral bud set, fruit quality, tissue nutrients, and soil properties, few treatment effects were observed across the 3-year study. Cold hardiness was only impacted once (8 Feb. 2020), and floral buds were overall hardy to extreme minimum winter temperatures for the region. This project showed that applying postharvest organic N as a liquid fertilizer had no negative consequences on productivity metrics for an early fruiting blueberry cultivar grown in a region with an extended growing season, thus providing growers with more flexibility when timing their fertilizer applications. Results may differ for other fertilizer sources, and further monitoring of soil NO3-N accumulation should be conducted to gain a better understanding of its dynamics and the potential for risks.

Establishing an efficient protoplast transient expression system for investigation of floral thermogenesis in aroids.

Floral thermogenesis is an important reproductive strategy for attracting pollinators. We developed essential biological tools for studying floral thermogenesis using two species of thermogenic aroids, Symplocarpus renifolius and Alocasia odora. Aroids contain many species with intense heat-producing abilities in their inflorescences. Several genes have been proposed to be involved in thermogenesis of these species, but biological tools for gene functional analyses are lacking. In this study, we aimed to develop a protoplast-based transient expression (PTE) system for the study of thermogenic aroids. Initially, we focused on skunk cabbage (Symplocarpus renifolius) because of its ability to produce intense as well as durable heat. In this plant, leaf protoplasts were isolated from potted and shoot tip-cultured plants with high efficiency (ca. 1.0 × 105/g fresh weight), and more than half of these protoplasts were successfully transfected. Using this PTE system, we determined the protein localization of three mitochondrial energy-dissipating proteins, SrAOX, SrUCPA, and SrNDA1, fused to green fluorescent protein (GFP). These three GFP-fused proteins were localized in MitoTracker-stained mitochondria in leaf protoplasts, although the green fluorescent particles in protoplasts expressing SrUCPA-GFP were significantly enlarged. Finally, to assess whether the PTE system established in the leaves of S. renifolius is applicable for floral tissues of thermogenic aroids, inflorescences of S. renifolius and another thermogenic aroid (Alocasia odora) were used. Although protoplasts were successfully isolated from several tissues of the inflorescences, PTE systems worked well only for the protoplasts isolated from the female parts (slightly thermogenic or nonthermogenic) of A. odora inflorescences. Our developed system has a potential to be widely used in inflorescences as well as leaves in thermogenic aroids and therefore may be a useful biological tool for investigating floral thermogenesis.

The Sensory and Cognitive Ecology of Nectar Robbing

Animals foraging from flowers must assess their environment and make critical decisions about which patches, plants, and flowers to exploit to obtain limiting resources. The cognitive ecology of plant-pollinator interactions explores not only the complex nature of pollinator foraging behavior and decision making, but also how cognition shapes pollination and plant fitness. Floral visitors sometimes depart from what we think of as typical pollinator behavior and instead exploit floral resources by robbing nectar (bypassing the floral opening and instead consuming nectar through holes or perforations made in floral tissue). The impacts of nectar robbing on plant fitness are well-studied; however, there is considerably less understanding, from the animal’s perspective, about the cognitive processes underlying nectar robbing. Examining nectar robbing from the standpoint of animal cognition is important for understanding the evolution of this behavior and its ecological and evolutionary consequences. In this review, we draw on central concepts of foraging ecology and animal cognition to consider nectar robbing behavior either when individuals use robbing as their only foraging strategy or when they switch between robbing and legitimate foraging. We discuss sensory and cognitive biases, learning, and the role of a variable environment in making decisions about robbing vs. foraging legitimately. We also discuss ways in which an understanding of the cognitive processes involved in nectar robbing can address questions about how plant-robber interactions affect patterns of natural selection and floral evolution. We conclude by highlighting future research directions on the sensory and cognitive ecology of nectar robbing.

GENOME-WIDE IDENTIFICATION AND COMPUTATIONAL CHARACTERIZATION OF THE NUCLEAR FACTOR-YC SUB-UNITS IN GRAIN AMARANTH (Amaranthus hypochondriacus)

Nuclear factor-Y (NF-Y) has been known as one of the plant-specific transcription factors that play key roles in numerous biological processes during the growth and development of plant species. In this study, a comprehensive analysis of NF-YC sub-units in grain amaranth (Amaranthus hypochondriacus) was carried out based on the bioinformatics approaches. Firstly, a total of five members of the NF-YC sub-units was reported in the grain amaranth. Its structural analyses revealed that the NF-YC sub-units were variable in physic-chemical properties, like protein sizes, molecular masses, isoelectric point, instability index, and grand average of hydropathy. Of our interest, the expression profiles of genes encoding NF-YC sub-units in various tissues\organs during the growth and development of grain amaranth. We found that three genes, including AhNF-YC01, AhNF-YC04, and AhNF-YC05 were highly expressed in leaf, root, floral, immature seed, and stem tissues. Interestingly, AhNF-YC05 was exclusively expressed in leaf and stem tissues. Taken together, our study could provide a solid understanding for further functional characterization of genes encoding NF-YC sub-units in grain amaranth.

Transgene pyramiding in wheat: Combination of deoxynivalenol detoxification with inhibition of cell wall degrading enzymes to contrast Fusarium Head Blight and Crown Rot

Fusarium Head Blight (FHB) and Crown Rot (FCR) are major diseases of wheat crops, causing extensive damages and mycotoxin contamination. In this work, we investigated the possibility to improve resistance to either or both diseases by combining different resistance mechanisms. To this aim, we stacked in the same wheat genotype transgenes controlling the DON-to-D3G conversion by specific UDP-glucosyltransferases (UGT) and the inhibition of cell wall degrading enzymes (CWDEs) by glycosidase inhibitors. We obtained: i) a durum wheat UGT+PMEI double-transgenic line constitutively expressing the HvUGT13248 and AcPMEI genes, coding for a barley UGT and a kiwi pectin methylesterase inhibitor, respectively; ii) a bread wheat UGT+PGIP line, expressing in floral tissues the HvUGT13248 gene and constitutively the PvPGIP2 gene, coding for a bean polygalacturonase inhibiting protein. We observed that both UGT+PMEI and UGT+PGIP plants exhibited increased resistance against Fusarium graminearum in FHB, further reducing by 10–20 % FHB symptoms as compared to the lines carrying the individual transgenes, and of up to 50 % as compared to wild-type plants. On the other hand, double-transgenic UGT+PMEI seedlings exhibited similar FCR symptoms as the UGT single transgenic line after infection with F. culmorum, indicating no contribution of the PMEI transgene to FCR resistance. This result is also supported by the inability of AcPMEI or PvPGIP2, constitutively expressed in durum wheat transgenic lines, to counteract F. graminearum in FCR. We also verified that F. graminearum produces PG and PME activity on infected wheat crown. We conclude that CWDEs inhibition combined with UGT-based DON detoxification contribute in an additive manner to limiting F. graminearum in FHB. Conversely, UGT-based DON detoxification is the only mechanism contributing to resistance observed against FCR. Indeed, the reinforcement of pectin does not enhance resistance against FCR.

Brassinosteroids regulate petal spur length in Aquilegia by controlling cell elongation.

Aquilegia produce elongated, three-dimensional petal spurs that fill with nectar to attract pollinators. Previous studies have shown that the diversity of spur length across the Aquilegia genus is a key innovation that is tightly linked with its recent and rapid diversification into new ranges, and that evolution of increased spur lengths is achieved via anisotropic cell elongation. Previous work identified a brassinosteroid response transcription factor as being enriched in the early developing spur cup. Brassinosteroids are known to be important for cell elongation, suggesting that brassinosteroid-mediated response may be an important regulator of spur elongation and potentially a driver of spur length diversity in Aquilegia. In this study, we investigated the role of brassinosteroids in the development of the Aquilegia coerulea petal spur. We exogenously applied the biologically active brassinosteroid brassinolide to developing petal spurs to investigate spur growth under high hormone conditions. We used virus-induced gene silencing and gene expression experiments to understand the function of brassinosteroid-related transcription factors in A. coerulea petal spurs. We identified a total of three Aquilegia homologues of the BES1/BZR1 protein family and found that these genes are ubiquitously expressed in all floral tissues during development, yet, consistent with the previous RNAseq study, we found that two of these paralogues are enriched in early developing petals. Exogenously applied brassinosteroid increased petal spur length due to increased anisotropic cell elongation as well as cell division. We found that targeting of the AqBEH genes with virus-induced gene silencing resulted in shortened petals, a phenotype caused in part by a loss of cell anisotropy. Collectively, our results support a role for brassinosteroids in anisotropic cell expansion in Aquilegia petal spurs and highlight the brassinosteroid pathway as a potential player in the diversification of petal spur length in Aquilegia.

Evaluation of Bt resistance in Helicoverpa zea (Lepidoptera: Noctuidae) strains using various Bt cotton plant tissues.

Diet-overlay bioassays suggest that Helicoverpa zea (Lepidoptera: Noctuidae) field populations have developed resistance to some of the Bt insecticidal proteins that are constituents of the pyramids expressed in the second and third generation Bt cotton technologies. Unfortunately, these bioassays are not always a reliable indicator for how a seemingly resistant population will perform in an actual cotton field, and thus, leaf tissue bioassays have been suggested as a method to better assess field performance. However, bollworm larvae typically prefer to feed on floral tissue rather than leaf tissue, and an alternative cotton structure type may be more ideal for use in plant tissue-based bioassays. A series of diet-overlay bioassays using Bt proteins and Bt cotton plant tissue were conducted with laboratory susceptible (Bz-SS) and resistant (Cry-RR, resistant to Cry1Ac and Cry2Ab) H. zea strains to determine if plant tissue overlays could detect resistance and which cotton plant structure type would be most ideal for use in bioassays. Results suggest that diet overlays using lyophilized plant tissue were able to detect resistance. Lyophilized tissue from white flowers was most ideal for use in bioassays, whereas tissue from non-Bt bolls and leaves affected larval health and behavior, confounding assay results. Overlays using white flower tissue could potentially be used to supplement Bt protein overlays and provide an improved assessment of larval performance on Bt cotton technologies. © 2021 Society of Chemical Industry.