Transcriptional regulation to enhance drought tolerance in plants: Co-expression of AhBTF3, AhNF-YA7 and EcSAP-ZF in rice and characterization of novel regulator, EcTAF6 in model system
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Date
2015-12-12
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
Drought adversely affects crop productivity in tropical countries. To improve crop
drought tolerance, modern approaches like molecular breeding and/or transgenesis are
used to pyramid traits. In this study, an attempt was made to manipulate transcriptional
regulation by co-expressing three stress responsive transcriptional regulators (TRs),
AhBTF3, AhNF-YA7 and EcSAP-ZF to enhance cellular tolerance under drought in rice.
The putative transgenic plants tolerant to glyphosate were confirmed for transgene
integration and expression. The T2 plants exhibited better growth performance under nonstress
conditions compared to wild type. The superior stress response of transgenic lines
was evidenced in excised leaf disc and seedling level assays under multiple abiotic
stresses. The selected lines had better pollen viability and grain yield than wild type, post
drought at reproductive stage. Superior T3 lines displayed enhanced tolerance to
transcription and translation inhibition, and organellar stresses. Six promising lines have
been forwarded to T4 generation for productivity analysis. Additionally, efforts were
made to prospect novel TRs from dry-land crop, finger millet, by analysing a drought
stressed leaf transcriptome data. This led to the identification and cloning of EcTAF6, a
subunit of transcription pre-initiation complex. Expression analysis of TAF6 in finger
millet and Brassica rapa revealed responsiveness to multiple stresses. Two splice
variants of EcTAF6, probably resulting from alternative splicing, were discovered in
stressed leaf cDNA. The functional characterisation of TAF6 by down regulation using
Virus Induced Gene Silencing approach in Nicotiana benthamiana, and Arabidopsis
attaf6 mutants demonstrated its relevance under stress. Transgenic Arabidopsis have been
developed to over-express EcTAF6 which are to be evaluated further. This study, for the
first time, indicated that TAF6 could be a key regulator in multiple stress response
networks. In conclusion, the study has demonstrated that basal transcriptional regulators
can be the novel candidates for enhancing cellular tolerance of crops under drought
conditions.
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