Hormone crosstalk and hormone-environment interaction
Hormones are chemical substances that can affect many cellular and developmental processes at low concentrations. The growth-inhibiting hormone, abscisic acid (ABA), and growth-promoting hormones, gibberellins (GA), play antagonistic roles in seed dormancy and germination, and the ABA/GA ratio determines whether a seed germinates or remains dormant. Other hormones, as well as nutrients and environmental cues, also regulate this developmental transition mainly through modulation of the ABA/GA ratio. Much debate in hormone biology revolves around specificity and redundancy of hormone signalling. While hormones can affect a given process through a signalling pathway that is specific for each hormone, the same biological process can be regulated by many hormones through independent (coregulation) or shared (crosstalk or cross-regulation) pathways. The Gazzarrini lab is interested in characterizing molecular mechanisms of hormone crosstalk an hormone-environment interaction during reproductive and seed development, as well as germination.
References:
Gazzarrini et al., 2004 (Dev Cell); Gazzarrini and Tsai, 2015 (Essays in Biochemistry); Chiu et al., 2016 (Plant J); Wu et al., 2019 (J Exp Bot)
The AFL network in plant reproduction, seed development, germination and stress response
The ABI3/FUS3/LEC2 B3-domain transcription factors, together with LEC1, are master regulators of seed maturation processes, including accumulation of seed storage compounds, establishment of dormancy and desiccation tolerance. Mutations in these genes, collectively called LAFL, profoundly affect seed maturation, resulting in strong reduction of seed storage compounds, premature germination of immature seeds and desiccation intolerance (lethality of dry seeds) in some mutants. Conversely, post-embryonic expression of LAFL induces embryonic traits and delays seed germination, plant growth and flowering. LAFL genes regulate these processes through modulation of hormone biosynthesis and/or signalling pathways, and some are themselves regulated by hormones at the transcriptional and/or post translational levels. LAFL genes are turned off during germination through chromatin remodelling mediated by VAL genes, which belong to a different clade of the B3-domain family. Spatiotemporal expression of LAFL genes is regulated at the transcriptional, post-translational and epigenetic level to ensure proper seed development. However, LAFL are also required to establish secondary dormancy and regulate seed yield during growth under unfavourable conditions, such as elevated temperature. Thus, LAFL-VAL constitute an ideal system to study hormonal- and environmental-dependent regulation of seed maturation and the timing of germination. We are currently investigating the transcriptional and epigenetic regulation LAFL genes and their interacting partners.
References
Gazzarrini et al., 2004 (Dev Cell); Lu et al., 2010 (Plant J); Tsai and Gazzarrini, 2012a (Plant J); Chiu et al., 2012 (BMC Plant Biol); Chan et al., 2017 (J Exp Bot); Duong et al., 2017 (J Exp Bot); Lepiniec et al., 2018 (Plant Reprod); Wu et al., 2020 (Plant Cell).
SnRK1-ABA interaction network during stress response
Carbohydrates regulate various aspects of plant growth through modulation of cell division and expansion. Besides playing essential roles as sources of energy for growth and as structural components of cells, carbohydrates also act as signaling molecules and regulate the timing of expression of developmental programs. Members of the Sucrose-non-fermenting1-Related Kinase1 (SnRK1) family are conserved in eukaryotes and are activated during metabolic stress to maintain energy homeostasis. The catalytic subunit SnRK1a1/AKIN10 is inactivated by PP2C phosphatases, negative regulators of ABA signalling, and phosphorylates FUS3 and bZIP transcription factors including positive regulators of ABA signalling such as ABI5. We have employed systems biology approaches to identify and characterize common targets of the SnRK1 and ABA signalling pathways, both of which are activated following exposure to stress. We are currently characterizing ABA-regulated substrates of the SnRK1a catalytic subunit and their roles in plant response to abiotic stresses.
References
Tsai and Gazzarrini, 2012 (Plant J); Tsai and Gazzarrini, 2014 (Front Plant Sci); Carianopol et al., 2020 (Commun Biol).
Hormones are chemical substances that can affect many cellular and developmental processes at low concentrations. The growth-inhibiting hormone, abscisic acid (ABA), and growth-promoting hormones, gibberellins (GA), play antagonistic roles in seed dormancy and germination, and the ABA/GA ratio determines whether a seed germinates or remains dormant. Other hormones, as well as nutrients and environmental cues, also regulate this developmental transition mainly through modulation of the ABA/GA ratio. Much debate in hormone biology revolves around specificity and redundancy of hormone signalling. While hormones can affect a given process through a signalling pathway that is specific for each hormone, the same biological process can be regulated by many hormones through independent (coregulation) or shared (crosstalk or cross-regulation) pathways. The Gazzarrini lab is interested in characterizing molecular mechanisms of hormone crosstalk an hormone-environment interaction during reproductive and seed development, as well as germination.
References:
Gazzarrini et al., 2004 (Dev Cell); Gazzarrini and Tsai, 2015 (Essays in Biochemistry); Chiu et al., 2016 (Plant J); Wu et al., 2019 (J Exp Bot)
The AFL network in plant reproduction, seed development, germination and stress response
The ABI3/FUS3/LEC2 B3-domain transcription factors, together with LEC1, are master regulators of seed maturation processes, including accumulation of seed storage compounds, establishment of dormancy and desiccation tolerance. Mutations in these genes, collectively called LAFL, profoundly affect seed maturation, resulting in strong reduction of seed storage compounds, premature germination of immature seeds and desiccation intolerance (lethality of dry seeds) in some mutants. Conversely, post-embryonic expression of LAFL induces embryonic traits and delays seed germination, plant growth and flowering. LAFL genes regulate these processes through modulation of hormone biosynthesis and/or signalling pathways, and some are themselves regulated by hormones at the transcriptional and/or post translational levels. LAFL genes are turned off during germination through chromatin remodelling mediated by VAL genes, which belong to a different clade of the B3-domain family. Spatiotemporal expression of LAFL genes is regulated at the transcriptional, post-translational and epigenetic level to ensure proper seed development. However, LAFL are also required to establish secondary dormancy and regulate seed yield during growth under unfavourable conditions, such as elevated temperature. Thus, LAFL-VAL constitute an ideal system to study hormonal- and environmental-dependent regulation of seed maturation and the timing of germination. We are currently investigating the transcriptional and epigenetic regulation LAFL genes and their interacting partners.
References
Gazzarrini et al., 2004 (Dev Cell); Lu et al., 2010 (Plant J); Tsai and Gazzarrini, 2012a (Plant J); Chiu et al., 2012 (BMC Plant Biol); Chan et al., 2017 (J Exp Bot); Duong et al., 2017 (J Exp Bot); Lepiniec et al., 2018 (Plant Reprod); Wu et al., 2020 (Plant Cell).
SnRK1-ABA interaction network during stress response
Carbohydrates regulate various aspects of plant growth through modulation of cell division and expansion. Besides playing essential roles as sources of energy for growth and as structural components of cells, carbohydrates also act as signaling molecules and regulate the timing of expression of developmental programs. Members of the Sucrose-non-fermenting1-Related Kinase1 (SnRK1) family are conserved in eukaryotes and are activated during metabolic stress to maintain energy homeostasis. The catalytic subunit SnRK1a1/AKIN10 is inactivated by PP2C phosphatases, negative regulators of ABA signalling, and phosphorylates FUS3 and bZIP transcription factors including positive regulators of ABA signalling such as ABI5. We have employed systems biology approaches to identify and characterize common targets of the SnRK1 and ABA signalling pathways, both of which are activated following exposure to stress. We are currently characterizing ABA-regulated substrates of the SnRK1a catalytic subunit and their roles in plant response to abiotic stresses.
References
Tsai and Gazzarrini, 2012 (Plant J); Tsai and Gazzarrini, 2014 (Front Plant Sci); Carianopol et al., 2020 (Commun Biol).
