How do brassinosteroids fit in bud outgrowth models?

Advance Access Publication 17 October 2023. OnlinePublShort stature crops were developed during the green revolution mainly due to their resistance to falling over (lodging), improved crop harvestability and management, and a greater proportion of biomass in the grains, leading to superior yield. These crops were disrupted in the gibberellin (GA) pathway, which caused the reduced height (Gao and Chu, 2020). GA disruption can introduce unwanted effects in other important traits such as fertility, leaf expansion, seed quality, and stress response (Gao and Chu, 2020). Hence, there are currently efforts to uncouple negative side effects of GA-related short stature or utilize alternative dwarfing pathways, such as brassinosteroids (BRs).Jack H. Kelly and Philip B. Brewe

Strigolactones, how are they synthesized to regulate plant growth and development?

Strigolactones (SLs) are multifunctional plant metabolites working not only as allelochemicals in the rhizosphere, but also as a novel class of hormones regulating growth and development in planta. To date, more than 30 SLs have been characterized, but the reason why plants produce structurally diverse SLs and the details of their biosynthetic pathway remain elusive. Recent studies using transcriptomics and reverse genetic techniques have paved the way to clarify the entire biosynthetic pathway of structurally diverse SLs. In this review, we discuss how various SLs are synthesized and what SL structural diversity means for plant growth and development.Kaori Yoneyama and Philip B Brewe

Investigations into the effects of cyclical rhythm and hormonal contraception on serum fat-mobilizing activity, glycerol, cholesterol and blood glucose.

The effects were investigated of cyclical rhythm and hormonal contraception on serum fat-mobilizing activity, glycerol, cholesterol and whole blood glucose during 2 menstrual cycles in a group of normally menstruating young women and a second group of young women using hormonal contraception. A control group of normal young men was also investigated. There was no evidence of any change in mean level of any of the parameters measured, among the follicular, ovulatory and luteal phases. No cyclical pattern was discernable in the male subjects. The mean value for serum cholesterol concentration in women using hormonal contraception was higher than the value for the untreated human female group. The overall mean value for serum glycerol concentration in the women was significantly (0.01 > P > 0.001) higher than the mean value obtaining in the men

Identification of new potential downstream transcriptional targets of the strigolactone pathway including glucosinolate biosynthesis.

Strigolactones regulate shoot branching and many aspects of plant growth, development, and allelopathy. Strigolactones are often discussed alongside auxin because they work together to inhibit shoot branching. However, the roles and mechanisms of strigolactones and how they act independently of auxin are still elusive. Additionally, there is still much in general to be discovered about the network of molecular regulators and their interactions in response to strigolactones. Here, we conducted an experiment in Arabidopsis with physiological treatments and strigolactone mutants to determine transcriptional pathways associated with strigolactones. The three physiological treatments included shoot tip removal with and without auxin treatment and treatment of intact plants with the auxin transport inhibitor, N-1-naphthylphthalamic acid (NPA). We identified the glucosinolate biosynthesis pathway as being upregulated across strigolactone mutants indicating strigolactone-glucosinolate crosstalk. Additionally, strigolactone application cannot restore the highly branched phenotype observed in glucosinolate biosynthesis mutants, placing glucosinolate biosynthesis downstream of strigolactone biosynthesis. Oxidative stress genes were enriched across the experiment suggesting that this process is mediated through multiple hormones. Here, we also provide evidence supporting non-auxin-mediated, negative feedback on strigolactone biosynthesis. Increases in strigolactone biosynthesis gene expression seen in strigolactone mutants could not be fully restored by auxin. By contrast, auxin could fully restore auxin-responsive gene expression increases, but not sugar signaling-related gene expression. Our data also point to alternative roles of the strigolactone biosynthesis genes and potential new signaling functions of strigolactone precursors. In this study, we identify a strigolactone-specific regulation of glucosinolate biosynthesis genes indicating that the two are linked and may work together in regulating stress and shoot ranching responses in Arabidopsis. Additionally, we provide evidence for non-auxinmediated feedback on strigolactone biosynthesis and discuss this in the context of sugar signaling.Alicia M. Hellens, Tinashe G. Chabikwa, Franziska Fichtner, Philip B. Brewer, Christine A. Beveridg

The response of nematodes to deep-sea CO2 sequestration : a quantile regression approach

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 57 (2010): 696-707, doi:10.1016/j.dsr.2010.03.003.One proposed approach to ameliorate the effects of global warming is sequestration of the greenhouse gas CO2 in the deep sea. To evaluate the environmental impact of this approach, we exposed the sediment-dwelling fauna at the mouth of the Monterey Submarine Canyon (3262 m) and a site on the nearby continental rise (3607 m) to CO2- rich water. We measured meiobenthic nematode population and community metrics after ~30-day exposures along a distance gradient from the CO2 source and with sediment depth to infer the patterns of mortality. We also compared the nematode response with that of harpacticoid copepods. Nematode abundance, average sediment depth, tail-group composition, and length: width ratio did not vary with distance from the CO2 source. However, quantile regression showed that nematode length and diameter increased in close proximity to the CO2 source in both experiments. Further, the effects of CO2 exposure and sediment depth (nematodes became more slender at one site, but larger at the other, with increasing depth in the sediment) varied with body size. For example, the response of the longest nematodes differed from those of average length. We propose that nematode body length and diameter increases were induced by lethal exposure to CO2-rich water and that nematodes experienced a high rate of mortality in both experiments. In contrast, copepods experienced high mortality rates in only one experiment suggesting that CO2 sequestration effects are taxon specific.The Department of Energy Office of Biological and Environmental Research supported this research under award numbers DE‐FG02‐05ER64070 and DE‐FG03‐01ER63065 and the U.S. Department of Energy, Fossil Energy Group (award DE‐FC26‐00NT40929). We also appreciate significant support provided by the Monterey Bay Aquarium Research Institute (project 200002)

Hydroxyl carlactone derivatives are predominant strigolactones in Arabidopsis

Strigolactones (SLs) regulate important aspects of plant growth and stress responses. Many diverse types of SL occur in plants, but a complete picture of biosynthesis remains unclear. In Arabidopsis thaliana , we have demonstrated that MAX1, a cytochrome P450 monooxygenase, converts carlactone (CL) into carlactonoic acid (CLA) and that LBO, a 2‐oxoglutarate‐dependent dioxygenase, can convert methyl carlactonoate (MeCLA) into a metabolite called [MeCLA + 16 Da]. In the present study, feeding experiments with deuterated MeCLAs revealed that [MeCLA + 16 Da] is hydroxymethyl carlactonoate (1'‐HO‐MeCLA). Importantly, this LBO metabolite was detected in plants. Interestingly, other related compounds, methyl 4‐hydroxycarlactonoate (4‐HO‐MeCLA) and methyl 16‐hydroxycarlactonoate (16‐HO‐MeCLA), were also found to accumulate in lbo mutants. 3‐HO‐, 4‐HO‐, and 16‐HO‐CL were detected in plants, but their expected corresponding metabolites, HO‐CLAs, were absent in max1 mutants. These results suggest that HO‐CL derivatives may be predominant SLs in Arabidopsis , produced through MAX1 and LBO.Kaori Yoneyama, Kohki Akiyama, Philip B. Brewer, Narumi Mori, Miyuki Kawano-Kawada, Shinsuke Haruta, Hisashi Nishiwaki, Satoshi Yamauchi, Xiaonan Xie, Mikihisa Umehara, Christine A. Beveridge, Koichi Yoneyama, Takahito Nomur

State of the world’s plants and fungi 2020

Kew’s State of the World’s Plants and Fungi project provides assessments of our current knowledge of the diversity of plants and fungi on Earth, the global threats that they face, and the policies to safeguard them. Produced in conjunction with an international scientific symposium, Kew’s State of the World’s Plants and Fungi sets an important international standard from which we can annually track trends in the global status of plant and fungal diversity

Initial bud outgrowth occurs independent of auxin flow from out of buds

Apical dominance is the process whereby the shoot tip inhibits the growth of axillary buds along the stem. It has been proposed that the shoot tip, which is the predominant source of the plant hormone auxin, prevents bud outgrowth by suppressing auxin canalization and export from axillary buds into the main stem. In this theory, auxin flow out of axillary buds is a prerequisite for bud outgrowth, and buds are triggered to grow by an enhanced proportional flow of auxin from the buds. A major challenge of directly testing this model is in being able to create a bud- or stem-specific change in auxin transport. Here we evaluate the relationship between specific changes in auxin efflux from axillary buds and bud outgrowth after shoot tip removal (decapitation) in the pea (Pisum sativum). The auxin transport inhibitor 1-N-naphthylphthalamic acid (NPA) and to a lesser extent, the auxin perception inhibitor p-chlorophenoxyisobutyric acid (PCIB), effectively blocked auxin efflux from axillary buds of intact and decapitated plants without affecting auxin flow in the main stem. Gene expression analyses indicate that NPA and PCIB regulate auxin-inducible, and biosynthesis and transport genes, in axillary buds within 3 h after application. These inhibitors had no effect on initial bud outgrowth after decapitation or cytokinin (benzyladenine; BA) treatment. Inhibitory effects of PCIB and NPA on axillary bud outgrowth only became apparent from 48 h after treatment. These findings demonstrate that the initiation of decapitation- and cytokinin-induced axillary bud outgrowth is independent of auxin canalization and export from the bud.Tinashe G. Chabikwa, Philip B. Brewer, and Christine A. Beveridg

Strigolactones: discovery of the elusive shoot branching hormone

The control of axillary bud outgrowth involves a network of hormonal signals and feedback regulation. A repressor of bud outgrowth that is central to the story has been missing since it was first postulated more than 70 years ago. This hormone moves upward in plant stems and can act as a long-distance messenger for auxin. Strigolactones, previously known as carotenoid-derived signals exuded from roots, fit the role of this elusive hormone. The discovery of branching inhibition by strigolactones will help solve many confusing aspects of branch control, including interactions with other signals, and is a great step forward toward uncovering the links between environment, genetics and plant form