Reactive oxygen species (ROS) are unstable reactive molecules that are toxic to cells. Regulation of ROS homeostasis is crucial to protect cells from dysfunction, senescence and death. In plant leaves, ROS are mainly generated from chloroplasts and are tightly temporally restricted by the circadian clock. However, little is known about how ROS homeostasis is regulated in non-photosynthetic organs, such as petals. Here, we showed that H2O2 levels exhibit typical circadian rhythmicity in rose (Rosa hybrida) petals, consistent with the measured respiratory rate. RNA-seq and functional screening identified a B-box gene, RhBBX28, whose expression was associated with H2O2 rhythms. Silencing RhBBX28 accelerated flower senescence and promoted H2O2 accumulation at night in petals, while overexpression of RhBBX28 had the opposite effects. RhBBX28 influenced the expression of various genes related to respiratory metabolism, including the TCA cycle and glycolysis, and directly repressed the expression of SUCCINATE DEHYDROGENASE 1, which plays a central role in mitochondrial ROS homeostasis. We also found that PHYTOCHROME INTERACTING FACTOR8 (RhPIF8) could activate RhBBX28 expression to control H2O2 levels in petals and thus flower senescence. Our results indicate that the circadian- controlled RhPIF8-RhBBX28 module is a critical player that controls flower senescence by governing mitochondrial ROS homeostasis in rose.
Parvularcula flava
was proposed as a novel member of genus
Parvularcula
in 2016. Some time earlier,
Aquisalinus flavus
has been proposed as a novel species of a novel genus named
Aquisalinus
. When comparing the 16S rRNA gene sequences of type strains
P. flava
NH6-79T and
A. flavus
D11M-2T, they showed 97.9 % sequence identity, much higher than the sequence identities 92.7–94.3 % between
P. flava
NH6-79T and type strains in the genus
Parvularcula
, indicating that the later proposed novel taxon
Parvularcula flava
need reclassification. The phylogenetic trees based on 16S rRNA gene sequences and genome sequences both showed that
P. flava
NH6-79T and
A. flavus
D11M-2T formed a separated branch away from strains in the genera
Parvularcula
,
Marinicaulis
and
Amphiplicatus
. The average amino acid identity and average nucleotide identity values of
P. flava
NH6-79T and
A. flavus
D11M-2T were 87.9 and 85.0 %, respectively, much higher than the values between
P. flava
NH6-79T and other closely related type strains (54.3 %–58.1 % and 68.6–70.4 %, respectively).
P. flava
NH6-79T and
A. flavus
D11M-2T also contained summed feature 8 (C18 : 1
ω6c and/or C18 : 1
ω7c) and C16 : 0 as major fatty acids, distinguishing them from other closely related taxa. Based on the results of the phylogenetic, comparative genomic and phenotypic analyses,
Parvularcula flava
should be reclassified as Aquisalinus luteolus nom. nov. and the description of genus
Aquisalinus
is emended.
A Gram-stain-positive, rod-shaped, strictly aerobic bacterial strain (Y6T) was isolated from a sewage sludge sample collected from a fisheries processing factory in Zhoushan, Zhejiang Province, PR China. The growth range of NaCl concentration was 0–6.0 % (w/v), with an optimum at 3.0 % (w/v). The temperature range for growth was 10–42 °C, with an optimum at 37 °C. The pH range for growth was pH 7.0–10.0, with an optimum at pH 9.0. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Y6T belonged to the genus
Nocardioides
and showed the highest sequence similarity of 97.8 % to
Nocardioides jishulii
dk3136T. The average nucleotide identity and in silico DNA–DNA hybridization values between strain Y6T and the reference strains were 76.9–81.2 % and 20.6–23.6 %, respectively. Chemotaxonomic analysis indicated that the sole respiratory quinone was MK-8(H4) and the predominant cellular fatty acids were iso-C16 : 0, 10-methyl-C17 : 0 and C18 : 1
ω9c. The polar lipid profile was composed of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, four unidentified phospholipids, three unidentified aminolipids and five unidentified lipids. The peptidoglycan was ll-2,6-diaminopimelic acid. On the basis of the phenotypic, genotypic, phylogenetic and chemotaxonomic features, strain Y6T is considered to represent a novel species, for which the name Nocardioides malaquae sp. nov. is proposed. The type strain is Y6T (=KCTC 49504T=MCCC 1K04765T).
AGAMOUS-LIKE 24 (AGL24) is a key gene regulating floral transition, but its involvement in flower organ identity remains largely unknown. In this study, we found that RhAGL24 is strongly related to petal and stamen development in rose. Its expression increases rapidly at the petal primordium development stage and maintains a high level until the complete differentiation stage. RhAGL24 silencing increases the number of malformed petals and decreases the number of stamens, indicating that this gene affects stamen petaloidy. RhAG (AGAMOUS), a class C gene associated with petal and stamen development, is downregulated in RhAGL24-silenced plants. Moreover, we found that RhAGL24 could directly bind to the promoter region of RhARF18 (AUXIN RESPONSE FACTORS 18), a regulator of RhAG. Our results suggested that RhAGL24-RhARF18 module regulates stamen petaloidy in rose and provide new insights into the function of AGL24 for plants.
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