Abstract
Diminishing global fresh water availability has focused research to elucidate mechanisms of water use in poplar, an economically important species. A GT-2 family trihelix transcription factor that is a determinant of water use efficiency (WUE), PtaGTL1 (GT-2 like 1), was identified in Populus tremula × P. alba (clone 717-IB4). Like other GT-2 family members, PtaGTL1 contains both N- and C-terminal trihelix DNA binding domains. PtaGTL1 expression, driven by the Arabidopsis thaliana AtGTL1 promoter, suppressed the higher WUE and drought tolerance phenotypes of an Arabidopsis GTL1 loss-of-function mutation (gtl1-4). Genetic suppression of gtl1-4 was associated with increased stomatal density due to repression of Arabidopsis STOMATAL DENSITY AND DISTRIBUTION1 (AtSDD1), a negative regulator of stomatal development. Electrophoretic mobility shift assays (EMSA) indicated that a PtaGTL1 C-terminal DNA trihelix binding fragment (PtaGTL1-C) interacted with an AtSDD1 promoter fragment containing the GT3 box (GGTAAA), and this GT3 box was necessary for binding. PtaGTL1-C also interacted with a PtaSDD1 promoter fragment via the GT2 box (GGTAAT). PtaSDD1 encodes a protein with 60% primary sequence identity with AtSDD1. In vitro molecular interaction assays were used to determine that Ca2+-loaded calmodulin (CaM) binds to PtaGTL1-C, which was predicted to have a CaM-interaction domain in the first helix of the C-terminal trihelix DNA binding domain. These results indicate that, in Arabidopsis and poplar, GTL1 and SDD1 are fundamental components of stomatal lineage. In addition, PtaGTL1 is a Ca2+-CaM binding protein, which infers a mechanism by which environmental stimuli can induce Ca2+ signatures that would modulate stomatal development and regulate plant water use.
Highlights
Populus species have many commercial uses such as lumber, composite materials, paper pulp, and woody perennial landscape plants [1]
We established that the GT-2 like 1 (GTL1) trihelix transcription factor is a stomatal development regulatory determinant that controls stomatal density through trans-repression of SDD1 expression [24]
Identification and structure of a poplar GT-2 family member, PtaGTL1 A BLASTp search analysis was conducted on proteins encoded in the Populus trichocarpa genome and seven proteins were identified based on primary sequence similarity and domain topology with AtGTL1 ([24]; Figure 1)
Summary
Populus species have many commercial uses such as lumber, composite materials, paper pulp, and woody perennial landscape plants [1]. We established that the GT-2 like 1 (GTL1) trihelix transcription factor is a stomatal development regulatory determinant that controls stomatal density through trans-repression of SDD1 expression [24]. Loss-of-function gtl1 mutations enhance WUE and drought tolerance due to a reduced transpiration rate that is correlated with a lowered stomatal density compared to wild-type plants [24].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
