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Summary Water deficit (drought stress) massively restricts plant growth and the yield of crops; reducing the deleterious effects of drought is therefore of high agricultural relevance. Drought triggers diverse cellular processes including the inhibition of photosynthesis, the accumulation of cell‐damaging reactive oxygen species and gene expression reprogramming, besides others. Transcription factors ( TF ) are central regulators of transcriptional reprogramming and expression of many TF genes is affected by drought, including members of the NAC family. Here, we identify the NAC factor JUNGBRUNNEN 1 ( JUB 1) as a regulator of drought tolerance in tomato ( Solanum lycopersicum ). Expression of tomato JUB 1 ( Sl JUB 1 ) is enhanced by various abiotic stresses, including drought. Inhibiting Sl JUB 1 by virus‐induced gene silencing drastically lowers drought tolerance concomitant with an increase in ion leakage, an elevation of hydrogen peroxide (H 2 O 2 ) levels and a decrease in the expression of various drought‐responsive genes. In contrast, overexpression of At JUB 1 from Arabidopsis thaliana increases drought tolerance in tomato, alongside with a higher relative leaf water content during drought and reduced H 2 O 2 levels. At JUB 1 was previously shown to stimulate expression of DREB 2A , a TF involved in drought responses, and of the DELLA genes GAI and RGL 1 . We show here that Sl JUB 1 similarly controls the expression of the tomato orthologs Sl DREB 1 , Sl DREB 2 and Sl DELLA . Furthermore, At JUB 1 directly binds to the promoters of Sl DREB 1 , Sl DREB 2 and Sl DELLA in tomato. Our study highlights JUB 1 as a transcriptional regulator of drought tolerance and suggests considerable conservation of the abiotic stress‐related gene regulatory networks controlled by this NAC factor between Arabidopsis and tomato.
Thirumalaikumar et al. (Thu,) studied this question.