Strigolactones (SLs) and karrikins (KARs) are both butenolide molecules that play essential roles in plant growth and development. SLs are phytohormones, with SLs having known functions within the plant they are produced in, while KARs are found in smoke emitted from burning plant matter and affect seeds and seedlings in areas of wildfire. It has been suggested that SL and KAR signaling may share similar mechanisms. The α/β hydrolases DWARF14 (D14) and KARRIKIN INSENSITIVE 2 (KAI2), which act as receptors of SL and KAR, respectively, both interact with the F-box protein MORE AXILLARY GROWTH 2 (MAX2) in order to target SUPPRESSOR OF MAX2 1 (SMAX1)-LIKE/D53 family members for degradation via the 26S proteasome. Recent reports suggest that SLs and/or KARs are also involved in regulating plant responses and adaptation to various abiotic stresses, particularly nutrient deficiency, drought, salinity, and chilling. There is also crosstalk with other hormone signaling pathways, including auxin, gibberellic acid (GA), abscisic acid (ABA), cytokinin (CK), and ethylene (ET), under normal and abiotic stress conditions. This review briefly covers the biosynthetic and signaling pathways of SLs and KARs, compares their functions in plant growth and development, and reviews the effects of any crosstalk between SLs or KARs and other plant hormones at various stages of plant development. We also focus on the distinct responses, adaptations, and regulatory mechanisms related to SLs and/or KARs in response to various abiotic stresses. The review closes with discussion on ways to gain additional insights into the SL and KAR pathways and the crosstalk between these related phytohormones.factors through interactions between the phytohormone regulatory networks via the perception and signal transduction originating at various receptors [20][21][22][23].Strigolactones (SLs) were originally isolated from root exudates of cotton and as seed germination stimulants from plants in the Orobanchaceae family that parasitize plant roots (Striga, Phelipanche, and Orobanche spp.) [24][25][26]. SLs normally control seed germination and seedling development [27], shoot branching [28-32], root architecture [33], and leaf senescence [34]. SLs also promote beneficial symbiotic relationships between host plants and mycorrhizal fungi [35,36]. The biosynthesis and signaling of SLs are regulated by various abiotic stress factors [37][38][39][40], including the recently reported SL involvement in responding to nutrient deprivation, drought, chilling and salinity [38,[40][41][42][43][44][45][46][47][48][49][50]. Such studies provide new insights into the novel roles SL signaling plays in the regulation of plant adaptation to adverse environmental conditions [51][52][53][54].Karrikins (KARs) are found in smoke released from the heating or combustion of plant material, after which they can stimulate the germination of dormant seeds [55][56][57][58]. KARs are also involved in the inhibition of hypocotyl elongation and in the promotion of cotyledon expansion and...
Flowering is a dynamic and synchronized process, the timing of which is finely tuned by various environmental signals. A T-DNA insertion mutant in Arabidopsis HEAT SHOCK PROTEIN-RELATED (AtHSPR) exhibited late-flowering phenotypes under both long-day (LD) and short-day (SD) conditions compared to the wild-type, while over-expression of AtHSPR promoted flowering. Exogenous application of gibberellin (GA) partially rescued the late-flowering mutant phenotype under both LD and SD conditions, suggesting that AtHSPR is involved in GA biosynthesis and/or the GA signaling that promotes flowering. Under SD or low-light conditions, the Athspr mutant exhibited late flowering together with reduced pollen viability and seed set, defective phenotypes that were partially rescued by GA treatment. qRT-PCR assays confirmed that GA biosynthetic genes were down-regulated, that GA catabolic genes were up-regulated, and that the levels of bioactive GA and its intermediates were decreased in Athspr under both SD and low-light/LD, further suggesting that AtHSPR could be involved in the GA pathway under SD and low-light conditions. Furthermore, AtHSPR interacted in vitro with OFP1 and KNAT5, which are transcriptional repressors of GA20ox1 in GA biosynthesis. Taken together, our findings demonstrate that AtHSPR plays a positive role in GA- and light intensity-mediated regulation of flowering and seed set.
Most mitochondrial proteins need to be imported from the cytosol. Over half of mitochondrial proteins are imported through the pre-sequence pathway that is controlled by the TOM complex in the outer membrane and the TIM23 complex in the inner membrane. It is unclear on the molecular level how proteins cross the mitochondrial double membranes through the TOM and TIM23 complexes. Here, we report the assembly of the active TOM-TIM23 supercomplex with translocating polypeptide substrates captured in the import pathway. Electron cryo-microscopy (Cryo-EM) analyses reveal that during translocation across the outer membrane, the polypeptide substrates pass through the center of the Tom40 channel while interacting with a glutamine-rich patch in the inner wall of Tom40. Structural and biochemical analyses show that the TIM23 complex contains a heterotrimer of the subunits Tim23, Tim17, and Mgr2 in the inner membrane. Tim17 and Mgr2 shield the polypeptide substrates from the lipid environment. The import pathway consists of two highly conserved residue patches of Tim17, one negatively charged patch at the entrance and one hydrophobic patch in the middle of the pathway. These data reveal an unexpected pre-sequence pathway mediated by the TOM-TIM23 supercomplex for facilitating protein import across the double membranes of mitochondria.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.