NAC transcription factor JUNGBRUNNEN1 enhances drought tolerance in tomato.

Venkatesh P Thirumalaikumar,Nikolay Mehterov,Vikas Devkar,Rengin Ozgur,Ismail Turkan,Bernd Mueller‐Roeber,Shawkat Ali,Salma Balazadeh

doi:10.1111/pbi.12776

Abstract

SummaryWater 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 JUNGBRUNNEN1 (JUB1) as a regulator of drought tolerance in tomato (Solanum lycopersicum). Expression of tomato JUB1 (SlJUB1) is enhanced by various abiotic stresses, including drought. Inhibiting SlJUB1 by virus‐induced gene silencing drastically lowers drought tolerance concomitant with an increase in ion leakage, an elevation of hydrogen peroxide (H2O2) levels and a decrease in the expression of various drought‐responsive genes. In contrast, overexpression of AtJUB1 from Arabidopsis thaliana increases drought tolerance in tomato, alongside with a higher relative leaf water content during drought and reduced H2O2 levels. AtJUB1 was previously shown to stimulate expression of DREB2A, a TF involved in drought responses, and of the DELLA genes GAI and RGL1. We show here that SlJUB1 similarly controls the expression of the tomato orthologs SlDREB1, SlDREB2 and SlDELLA. Furthermore, AtJUB1 directly binds to the promoters of SlDREB1, SlDREB2 and SlDELLA in tomato. Our study highlights JUB1 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.

Highlights

Water deficit represents one of the most significant abiotic stresses limiting plant growth, development and productivity
We investigated the function of the NAC transcription factor JUNGBRUNNEN1 (JUB1) for the response of tomato to drought stress
We demonstrate that tomato plants with reduced expression of SlJUB1 (Solanum lycopersicum JUB1; Solyc05G021090), the closest homologue to Arabidopsis AtJUB1, are more sensitive to drought than control plants and exhibit a higher level of oxidative stress

Summary

Introduction

Water deficit (drought) represents one of the most significant abiotic stresses limiting plant growth, development and productivity. Drought triggers several responses in plants including a cessation of shoot growth, the inhibition of the initiation of new leaves and the promotion of senescence in older leaves leading to a remarkable decrease in canopy size and crop yield (Degenkolbe et al, 2009; Harris et al, 2007; Martınez et al, 2007; Rivero et al, 2007). The coordinated regulation of gene expression represents one such sophisticated response to drought stress. Water deficit triggers a wide-scale reprogramming of the transcriptome whereby transcription factors (TFs), and the gene regulatory networks (GRNs) they control, are of central importance (Chen et al, 2016; Joshi et al, 2016; Rabara et al, 2014; Todaka et al, 2015; Vermeirssen et al, 2014)

Results

Discussion

Conclusion