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New hope for creating drought-resistant plants

Drought is an increasing problem all over the world and the main reason for crop failure, thus there is a need to develop plants that are highly resistant to drought. We have found targeting of the NatA enzyme to be a way to develop highly drought resistant plants since NatA controls the stress imposed on plants by drought.

New hope for creating drought-resistant plants
NatA depleted plants are resistant towards drought. NatA depleted plants (amiNaa10 and amiNaa15 plants) have a reduced growth (pattern) but were highly resistant to drought stresses and retained 95% of the water content of the leaves after a prolonged drought period (A). Wild type plants died after 20 days of drought and could not be rescued with resupply of water. NatA depleted plants did not show visible symptoms associated with water deficiency and after resupply with water, all NatA depleted plants continued to grow and produced viable seeds (B).

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N-terminal acetylation is a common modification occurring on more than 80% of all human proteins. N-terminal acetyltransferase enzymes (NATs) catalyze this reaction and attach a small label (an acetyl group) to the very first amino acid (the N-terminus) of the newly produced protein. To date, six NATs have been identified (NatA-F), where NatA is the major NAT complex by acetylating a large number of cellular proteins. NatA has been implicated in cancer development as well as other diseases and demonstrate the physiological significance of N-terminal acetylation.

This week, a molecular link between N-terminal acetylation and drought tolerance was presented in Nature Communications. A team led by Markus Wirtz and his group at the University of Heidelberg, along with collaborators from Institut des Sciences du Végégal, University of Stavanger, the Max Planck Institute for Chemical Ecology, and University of Bergen Department of Molecular Biology researchers Line M. Myklebust and Thomas Arnesen (http://www.uib.no/rg/nat) revealed essential functions of NatA for control and regulation of metabolism, development and cellular stress responses in plants. Plant NatA target 50% of all soluble proteins in leaves, and both composition and substrate specificity demonstrated NatA to be evolutionarily conserved within higher eukaryotes. The plant NatA complex was shown to be essential for proper embryogenesis in plants. Depletion of the catalytically active subunit Naa10 or the auxiliary subunit Naa15 in the NatA complex resulted in a reduced degree of N-terminal acetylation of the proteome and decreased plant growth but increased adapted total root length with improved water uptake compared to wild type plants. Interestingly, this was shown to contribute to cellular surveillance during prolonged drought in plants and through activation and control of the hormone abscisic acid (ABA), a hormone regulating transcription of drought-stress related genes and root branching. In fact, this is the first study describing a hormone-regulated adaption of the N-acetylome upon environmental changes. N-terminal acetylation by NatA was demonstrated as an ABA regulated dynamic process, where NatA was shown to act down-stream of ABA during induction of the drought stress response.

Drought is the main reason for crop failure in the world agriculture. We here demonstrate N-terminal acetylation by NatA as a vital hormone-regulated switch during drought stress, a mechanism that could be used to genetically engineer plants more resistant towards water limitation, a need that will become more and more evident as a result of global warming.

 

The NAT group receives funding from Bergen Research Foundation, The Research Council of Norway, The Norwegian Cancer Society and Western Norway Regional Health Authority.