A plant SUMO ligase regulates the protein stability of a chromatin remodeling factor in root development.
Chromatin remodeling is essential for gene expression regulation in plant development and ...response to stresses. Brahma (BRM) is a conserved ATPase in the SWI/SNF chromatin remodeling complex and is involved in various biological processes in plant cells, but the regulation mechanism on BRM protein remains unclear. Here, we report that BRM interacts with AtMMS21, a SUMO ligase in Arabidopsis (
Arabidopsis thaliana
). The interaction was confirmed in different approaches in vivo and in vitro. The mutants of
BRM
and
AtMMS21
displayed a similar defect in root development. In the
mms21-1
mutant, the protein level of BRM-GFP was significantly lower than that in wild type, but the RNA level of
BRM
did not change. Biochemical evidence indicated that BRM was modified by SUMO3, and the reaction was enhanced by AtMMS21. Furthermore, overexpression of wild-type AtMMS21 but not the mutated AtMMS21 without SUMO ligase activity was able to recover the stability of BRM in
mms21-1
. Overexpression of
BRM
in
mms21-1
partially rescued the developmental defect of roots. Taken together, these results supported that AtMMS21 regulates the protein stability of BRM in root development.
The transcriptional regulator MYB30 links systemic reactive oxygen species signaling with systemic acquired acclimation during the response of Arabidopsis to excess light stress.
Systemic acquired ...acclimation (SAA) is a key biological process essential for plant survival under conditions of abiotic stress. SAA was recently shown to be controlled by a rapid systemic signaling mechanism termed the reactive oxygen species (ROS) wave in Arabidopsis (
Arabidopsis thaliana
). MYB30 is a key transcriptional regulator mediating many different biological processes. MYB30 was found to act downstream of the ROS wave in systemic tissues of Arabidopsis in response to local high light (HL) stress treatment. However, the function of MYB30 in systemic signaling and SAA is unknown. To determine the relationship among MYB30, the ROS wave, and systemic acclimation in Arabidopsis, the SAA response to HL stress of
myb30
mutants and wild-type plants was determined. Although
myb30
plants were found to display enhanced rates of ROS wave propagation and their local tissues acclimated to the HL stress, they were deficient in SAA to HL stress. Compared to wild type, the systemic transcriptomic response of
myb30
plants was also deficient, lacking in the expression of over 3,500 transcripts. A putative set of 150 core transcripts directly associated with MYB30 function during HL stress was determined. Our study identifies MYB30 as a key regulator that links systemic ROS signaling with systemic transcriptomic responses, SAA, and plant acclimation to HL stress. In addition, it demonstrates that plant acclimation and systemic ROS signaling are interlinked and that the lack of systemic acclimation drives systemic ROS signaling to occur at faster rates, suggesting a feedback mechanism (potentially involving MYB30) between these two processes.
Characterization of the TCP4-WRI1 complex regulating Arabidopsis seed oil biosynthesis expands our understanding of WRI1-interacting factors and describes a further role for TCP transcription ...factors.
Cross-family transcription factor (TF) interactions play critical roles in the regulation of plant developmental and metabolic pathways. WRINKLED1 (WRI1) is a key TF governing oil biosynthesis in plants. However, little is known about WRI1-interacting factors and their roles in oil biosynthesis. We screened a TF library using Arabidopsis (
Arabidopsis thaliana
) WRI1 (AtWRI1) as bait in yeast two-hybrid assays and identified three TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) family TFs, namely TCP4, TCP10, and TCP24, as AtWRI1-interacting partners. The physical interaction between AtWRI1 and TCPs was further validated using bimolecular fluorescence complementation assays. TCPs play important roles in various plant developmental processes; however, their involvement in fatty acid biosynthesis was not previously known. Coexpression of TCP4, but not TCP10 or TCP24, with AtWRI1 reduced AtWRI1-mediated oil biosynthesis in
Nicotiana benthamiana
leaves. Transcriptomic analysis in transgenic Arabidopsis plants with enhanced TCP4 activity engineered by expressing
rTCP4
(i.e. miR319-resistant
TCP4
) revealed that AtWRI1 target genes were significantly repressed. TCP4 expression is strongly correlated with AtWRI1 during embryo development. A
tcp4
loss-of-function mutant, the
jaw-D
mutant with a strong reduction of
TCP4
expression, and a
tcp2 tcp4 tcp10
triple mutant accumulated more seed oil than wild-type Arabidopsis. In addition, TCP4 repressed the AtWRI1-mediated transactivation of the promoters of fatty acid biosynthetic genes. Collectively, our findings suggest that TCP4 represses fatty acid biosynthetic gene expression through interaction with AtWRI1, leading to a reduction of AtWRI1-mediated seed oil accumulation.
The COVID-19 pandemic sparked efforts across the globe to implement wastewater surveillance for SARS-CoV-2.
New York State (NYS) established the NYS Wastewater Surveillance Network to estimate the ...levels of COVID-19 community risk and to provide an early indication of SARS-CoV-2 transmission trends. The network is designed to provide a better understanding of public health burdens and to assist health departments to respond effectively to public health threats.
Wastewater surveillance across NYS increased from sporadic and geographically spare in 2020 to routine and widespread in 2022, reaching all 62 counties in the state and covering 74% of New Yorkers. The network team focused on engaging local health departments and wastewater treatment plants to provide wastewater samples, which are then analyzed through a network-affiliated laboratory. Both participating local health departments and wastewater treatment plants receive weekly memos on current SARS-CoV-2 trends and levels. The data are also made publicly available at the state dashboard.
Using standard indicators to evaluate infectious disease surveillance systems, the NYS Wastewater Surveillance Network was assessed for accuracy, timeliness, and completeness during the first year of operations. We observed 96.5% sensitivity of wastewater to identify substantial/high COVID-19 transmission and 99% specificity to identify low COVID-19 transmission. In total, 80% of results were reported within 1 day of sample collection and were published on the public dashboard within 2 days of sample collection. Among participating wastewater treatment plants, 32.5% provided weekly samples with zero missing data, 31% missed 1 or 2 weeks, and 36.5% missed 3 or more weeks.
The NYS Wastewater Surveillance Network continues to be a key component of the state and local health departments' pandemic response. The network fosters prompt public health actions through real-time data, enhancing the preparedness capability for both existing and emerging public health threats.
A mixed-inoculum, “select and resequence” approach efficiently assays for strain-specific effects of host mutations in nodule-specific genes.
Genetic studies of legume symbiosis with nitrogen-fixing ...rhizobial bacteria have traditionally focused on nodule and nitrogen-fixation phenotypes when hosts are inoculated with a single rhizobial strain. These approaches overlook the potential effect of host genes on rhizobial fitness (i.e. how many rhizobia are released from host nodules) and strain-specific effects of host genes (i.e. genome × genome interactions). Using
Medicago truncatula
mutants in the recently described nodule-specific PLAT domain (
NPD
) gene family, we show how inoculating plants with a mixed inoculum of 68 rhizobial strains (
Ensifer meliloti
) via a select-and-resequence approach can be used to efficiently assay host mutants for strain-specific effects of late-acting host genes on interacting bacteria. The deletion of a single
NPD
gene (
npd2
) or all five members of the
NPD
gene family (
npd1
–
5
) differentially altered the frequency of rhizobial strains in nodules even though
npd2
mutants had no visible nodule morphology or N-fixation phenotype. Also,
npd1
–
5
nodules were less diverse and had larger populations of colony-forming rhizobia despite their smaller size. Lastly,
NPD
mutations disrupt a positive correlation between strain fitness and wild-type host biomass. These changes indicate that the effects of NPD proteins are strain dependent and that
NPD
family members are not redundant with regard to their effects on rhizobial strains. Association analyses of the rhizobial strains in the mixed inoculation indicate that rhizobial genes involved in chromosome segregation, cell division, GABA metabolism, efflux systems, and stress tolerance play an important role in the strain-specific effects of
NPD
genes.
Under simulated high light, diel growth conditions, the photosynthetic apparatus of Chlamydomonas reinhardtii exhibits an almost constitutive photoprotection capacity through non-photochemical ...quenching.
The photosynthetic apparatus must be able to withstand light conditions that exceed its capacity for carbon fixation. Photosynthetic organisms developed nonphotochemical quenching (NPQ), a process that dissipates excess absorbed light energy as heat and limits the production of reactive oxygen species and cellular damage. In the green alga
Chlamydomonas reinhardtii
, the LHCSR pigment-binding proteins are essential for NPQ. These complexes are not constitutively present in the thylakoid membranes; however, in laboratory conditions their expression depends on prior high light exposure of cells. To investigate the role of NPQ, we measured cells grown under a day-night cycle with a high light peak at mid-day. LHCSRs are present and NPQ is active consistently throughout the day, likely due to their slow degradation in vivo. This suggests that in physiologically relevant conditions,
Chlamydomonas
cells are prepared to immediately activate photoprotection, as is the case in vascular plants. We further reveal that state transitions are fully functional under these conditions and that PsbS is highly expressed throughout the day, suggesting it might have a more impactful role than previously thought.
Seedling organs show autonomy as well as interdependency in their ability to respond to elevated temperatures.
Plants have a remarkable capacity to adjust their growth and development to elevated ...ambient temperatures. Increased elongation growth of roots, hypocotyls, and petioles in warm temperatures are hallmarks of seedling thermomorphogenesis. In the last decade, significant progress has been made to identify the molecular signaling components regulating these growth responses. Increased ambient temperature utilizes diverse components of the light sensing and signal transduction network to trigger growth adjustments. However, it remains unknown whether temperature sensing and responses are universal processes that occur uniformly in all plant organs. Alternatively, temperature sensing may be confined to specific tissues or organs, which would require a systemic signal that mediates responses in distal parts of the plant. Here, we show that Arabidopsis (
Arabidopsis thaliana
) seedlings show organ-specific transcriptome responses to elevated temperatures and that thermomorphogenesis involves both autonomous and organ-interdependent temperature sensing and signaling. Seedling roots can sense and respond to temperature in a shoot-independent manner, whereas shoot temperature responses require both local and systemic processes. The induction of cell elongation in hypocotyls requires temperature sensing in cotyledons, followed by the generation of a mobile auxin signal. Subsequently, auxin travels to the hypocotyl, where it triggers local brassinosteroid-induced cell elongation in seedling stems, which depends upon a distinct, permissive temperature sensor in the hypocotyl.
Enlarged mitochondria with increased rates of alternative respiration may account for the striking heat-producing ability of male cones in the gymnosperm Cycas revoluta.
Cone thermogenesis is a ...widespread phenomenon in cycads and may function to promote volatile emissions that affect pollinator behavior. Given their large population size and intense and durable heat-producing effects, cycads are important organisms for comprehensive studies of plant thermogenesis. However, knowledge of mitochondrial morphology and function in cone thermogenesis is limited. Therefore, we investigated these mitochondrial properties in the thermogenic cycad species
Cycas revoluta
. Male cones generated heat even in cool weather conditions. Female cones produced heat, but to a lesser extent than male cones. Ultrastructural analyses of the two major tissues of male cones, microsporophylls and microsporangia, revealed the existence of a population of mitochondria with a distinct morphology in the microsporophylls. In these cells, we observed large mitochondria (cross-sectional area of 2 μm
2
or more) with a uniform matrix density that occupied >10% of the total mitochondrial volume. Despite the size difference, many nonlarge mitochondria (cross-sectional area <2 μm
2
) also exhibited a shape and a matrix density similar to those of large mitochondria. Alternative oxidase (AOX) capacity and expression levels in microsporophylls were much higher than those in microsporangia. The
AOX
genes expressed in male cones revealed two different
AOX
complementary DNA sequences:
CrAOX1
and
CrAOX2
. The expression level of
CrAOX1
mRNA in the microsporophylls was 100 times greater than that of
CrAOX2
mRNA. Collectively, these results suggest that distinctive mitochondrial morphology and CrAOX1-mediated respiration in microsporophylls might play a role in cycad cone thermogenesis.
Comprehensive genomic analysis and experimental verification provide conclusive evidence that red algal terpenes are biosynthesized by microbial-type terpene synthases.
Red algae (Rhodophyta) and ...land plants belong to the monophyletic clade Archaeplastida, and taxa of both groups are rich producers of terpene secondary metabolites. The terpene carbon skeletons of land plants are made by two types of terpene synthases: typical plant terpene synthases and microbial-type terpene synthases (MTPSLs); however, terpene biosynthesis in red algae is poorly understood. By systematic sequence analysis of seven genomes and 34 transcriptomes of red algae,
MTPSL
homologs were identified within one genome and two transcriptomes, whereas no homolog of typical plant terpene synthase genes was found. Phylogenetic analysis showed that red algae MTPSLs group with bacterial terpene synthases. Analysis of the genome assembly and characterization of neighboring genes demonstrated red algal
MTPSLs
to be bona fide red algal genes and not microbial contaminants.
MTPSL
genes from
Porphyridium purpureum
and
Erythrolobus australicus
were characterized via heterologous expression in
Escherichia coli
and demonstrated to have sesquiterpene synthase activities. We detected a number of volatile sesquiterpenes in the headspace of
P. purpureum
and
E. australicus
cultures, most identical to the in vitro products of the respective MTPSLs. Expression of the
MTPSL
gene in
P. purpureum
was found to be induced by methyl jasmonate, suggesting a role for this gene in host defense. In summary, this study indicates that the formation of terpene carbon skeletons in red algae is carried out by MTPSLs that are phylogenetically unrelated to typical plant terpene synthases and most likely originated in Rhodophyta via horizontal gene transfer from bacteria.
Auxin and key flower meristem genes play a pivotal role in patterning of the capitulum, a key innovation that taxonomically defines the daisy family.
Nature often creates complex structures by ...rearranging pre-existing units. One such example is the flower head (capitulum) in daisies, where a group of flowers (florets) and phyllaries (modified bracts) are arranged to superficially mimic a single flower. The capitulum is a key taxonomical innovation that defines the daisy family (Asteraceae), the largest flowering plant group. However, patterning mechanisms underlying its structure remain elusive. Here, we show that auxin, a plant hormone, provides a developmental patterning cue for the capitulum. During capitulum development, a temporal auxin gradient occurs, regulating the successive and centripetal formation of distinct florets and phyllaries. Disruption of the endogenous auxin gradient led to homeotic conversions of florets and phyllaries in the capitulum. Furthermore, auxin regulates floral meristem identity genes, such as
Matricaria inodora RAY2
and
M
.
inodora LEAFY
, which determine floret and phyllary identity. This study reveals the mechanism of capitulum patterning and highlights how common developmental tools, such as hormone gradients, have independently evolved in plants and animals.
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