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Endogenous levels of some molecules, such as polyamines (PAs) and auxin, can be associated with the control of shoot and root development. The effects of 6-benzyladenine (BA), putrescine (Put) and the auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) on the development of Cedrela fissilis shoots, as well as the effects on endogenous alterations in PAs and variations in protein abundance, were investigated. Furthermore, the effects of Put and TIBA on ex vitro root development and the endogenous content of PAs were investigated. The BA + Put combined with TIBA treatment promoted an inhibition of shoot growth from cotyledonary nodal segments, decreasing endogenous total free PA levels and increasing IAA-free content compared to shoots treated with BA + Put without TIBA. A comparative proteomic analysis of BA + Put + TIBA-treated shoots showed reduced accumulation of proteins mainly related to cytoskeleton organization, carbon metabolism, and photosynthesis and increased accumulation of proteins related to the degradation of valine, leucine and isoleucine compared to those without TIBA. The percentage and number of rooted shoots were significantly reduced by Put + TIBA treatment, showing that auxin inhibitors and not Put are responsible for the decrease in rooting. These results show that the combination of BA + Put with the auxin transport inhibitor TIBA interferes with endogenous PA metabolism and alters protein abundance, thereby altering shoot development. Moreover, Put is not related to rooting induction in C. fissilis.Key message: Effects of 2,3,5-triiodobenzoic acid on modulating the in vitro growth response of axillary buds and adventitious rooting of Cedrela fissilis. [ABSTRACT FROM AUTHOR]

Key message: The overexpression of the soybean GmEXPA1 gene reduces plant susceptibility to M. incognita by the increase of root lignification. Plant expansins are enzymes that act in a pH-dependent manner in the plant cell wall loosening and are associated with improved tolerance or resistance to abiotic or biotic stresses. Plant-parasitic nematodes (PPN) can alter the expression profile of several expansin genes in infected root cells. Studies have shown that overexpression or downregulation of particular expansin genes can reduce plant susceptibility to PPNs. Root-knot nematodes (RKN) are obligate sedentary endoparasites of the genus Meloidogyne spp. of which M. incognita is one of the most reported species. Herein, using a transcriptome dataset and real-time PCR assays were identified an expansin A gene (GmEXPA1; Glyma.02G109100) that is upregulated in the soybean nematode-resistant genotype PI595099 compared to the susceptible cultivar BRS133 during plant parasitism by M. incognita. To understand the role of the GmEXPA1 gene during the interaction between soybean plant and M. incognita were generated stable A. thaliana and N. tabacum transgenic lines. Remarkably, both A. thaliana and N. tabacum transgenic lines overexpressing the GmEXPA1 gene showed reduced susceptibility to M. incognita. Furthermore, plant growth, biomass accumulation, and seed yield were not affected in these transgenic lines. Interestingly, significant upregulation of the NtACC oxidase and NtEFE26 genes, involved in ethylene biosynthesis, and NtCCR and Nt4CL genes, involved in lignin biosynthesis, was observed in roots of the N. tabacum transgenic lines, which also showed higher lignin content. These data suggested a possible link between GmEXPA1 gene expression and increased lignification of the root cell wall. Therefore, these data support that engineering of the GmEXPA1 gene in soybean offers a powerful biotechnology tool to assist in RKN management. [ABSTRACT FROM AUTHOR]

Main conclusion: The overexpression of the GmGlb1-1 gene reduces plant susceptibility to Meloidogyne incognita. Non-symbiotic globin class #1 (Glb1) genes are expressed in different plant organs, have a high affinity for oxygen, and are related to nitric oxide (NO) turnover. Previous studies showed that soybean Glb1 genes are upregulated in soybean plants under flooding conditions. Herein, the GmGlb1-1 gene was identified in soybean as being upregulated in the nematode-resistant genotype PI595099 compared to the nematode-susceptible cultivar BRS133 during plant parasitism by Meloidogyne incognita. The Arabidopsis thaliana and Nicotiana tabacum transgenic lines overexpressing the GmGlb1-1 gene showed reduced susceptibility to M. incognita. Consistently, gall morphology data indicated that pJ2 nematodes that infected the transgenic lines showed developmental alterations and delayed parasitism progress. Although no significant changes in biomass and seed yield were detected, the transgenic lines showed an elongated, etiolation-like growth under well-irrigation, and also developed more axillary roots under flooding conditions. In addition, transgenic lines showed upregulation of some important genes involved in plant defense response to oxidative stress. In agreement, higher hydrogen peroxide accumulation and reduced activity of reactive oxygen species (ROS) detoxification enzymes were also observed in these transgenic lines. Thus, based on our data and previous studies, it was hypothesized that constitutive overexpression of the GmGlb1-1 gene can interfere in the dynamics of ROS production and NO scavenging, enhancing the acquired systemic acclimation to biotic and abiotic stresses, and improving the cellular homeostasis. Therefore, these collective data suggest that ectopic or nematode-induced overexpression, or enhanced expression of the GmGlb1-1 gene using CRISPR/dCas9 offers great potential for application in commercial soybean cultivars aiming to reduce plant susceptibility to M. incognita. [ABSTRACT FROM AUTHOR]

Investigation of the biochemical and molecular changes during rooting in woody species can reveal how specific molecules are involved in adventitious root (AR) induction. We investigated the effects of indole butyric acid (IBA) and inhibitors of polar auxin transport and auxin signaling on ex vitro rooting of micropropagated shoots of Cedrela fissilis and evaluated the proteomic profile and endogenous contents of indole acetic acid (IAA) during AR initiation. We observed that exogenous IBA was not necessary for ex vitro rooting, and root induction was significantly reduced by auxin signaling (p-chlorophenoxyisobutyric acid—PCIB) and polar auxin transport (triiodobenzoic acid—TIBA) inhibitors. The presence of meristematic cells and the formation of meristematic centers in the base of shoot cuttings at 3 days of rooting are necessary for AR formation. The accumulation of cell division- and auxin-related proteins and the presence of unique proteins related to cell wall modification in shoot cuttings at 3 days of rooting were associated with higher IAA contents and AR initiation. In addition, an accumulation of proteins related to dephosphorylation, glycolytic and tricarboxylic acid cycle pathways and a reduction in the accumulation of proteins from isoflavonoid metabolism were associated with the promotion of AR initiation. These results show the relevance of these proteins for AR initiation in this species. This is the first study showing the involvement of protein accumulation and endogenous IAA contents in adventitious rooting initiation in C. fissilis, an easily rooted endangered woody species from the Brazilian rainforest. Key message: Auxin contents and proteomic analyses during adventitious rooting of in vitro propagated Cedrela fissilis shoots. [ABSTRACT FROM AUTHOR]

Araucaria angustifolia (Bertol.) O. Kuntze exhibits dimorphism in its stem structure, where the trunk is orthotropic and branches and branchlets (primary and secondary branches) are plagiotropic. These stems exhibit different behavior when used for vegetative propagation, and only segments of trunk can form a complete plant. The physiological and biochemical mechanisms that characterize these stems are still little known. The aim of this study was to describe the free amino acid profiles in trunks, branches, and branchlets of A. angustifolia. Segments of 5 cm in length were excised from young individuals below the stem apex. The needles were removed and samples were frozen and lyophilized. The determinations were made by high-performance liquid chromatography, and the results were expressed as µg/g fresh weight (FW). The trunks and branches had the highest content of total amino acids, which were 112.23 ± 20.57 µg/g FW and 111.97 ± 27.78 µg/g FW, respectively. The amino acids—glutamine, aspartate and γ-aminobutyric acid and tyrosine—were noticeably higher in the three types of stems. In the trunk, a higher amount of asparagine and tryptophan, was also detected. Glutamic acid and glutamine were found in higher quantities in the branches. The branchlets had very low total amino acid content (30.79 ± 4.19 µg/g FW), wherein asparagine is the only amino acid not detected. Thus, it was observed that the profile of the free amino acid differs among trunks, branches, and branchlets in A. angustifolia, indicating that they perform different functions. [ABSTRACT FROM AUTHOR]

Ethylene and polyamines (PAs) are two phytohormones that play important roles during in vitro morphogenesis of several plant species. The interaction between ethylene and PAs has been of interest because both have S-adenosylmethionine as a precursor. To study the influence of ethylene and PAs on in vitro morphogenesis of an ornamental pepper, we added an ethylene scavenger, PAs, a PA inhibitor, and compounds that affect ethylene biosynthesis and activity to the regeneration medium. Regeneration frequencies increased in response to treatment with ethylene inhibitors (aminoethoxyvinylglycine and silver thiosulfate) and an ethylene scavenger (mercury perchlorate). Treatment with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid reduced the regeneration frequency, increased callus formation, and increased ethylene levels; similar results were obtained in response to treatment with the PA inhibitor methylglyoxal-bis(guanylhydrazone). By contrast, treatment with PAs (particularly spermidine and spermine) decreased ethylene levels, increased the regeneration frequency, and increased shoot bud formation. These results suggest a coordinated regulation of ethylene and polyamines because the suppression of ethylene levels using ethylene inhibitors, polyamines, or mercury perchlorate increased the in vitro regeneration frequency and morphogenic responses of Capsicum annuum L. [ABSTRACT FROM AUTHOR]