ATHB17 enhances stress tolerance by coordinating photosynthesis associated nuclear gene and ATSIG5 expression in response to abiotic stress

Ping Zhao,Jie Wu,Lin-Hui Yu,Cong-Zhao Zhou,Ping Xu,Cheng-Bin Xiang,Rong Cui,Jie-Li Mao,Yu Chen

doi:10.1038/srep45492

Abstract

Photosynthesis is sensitive to environmental stress and must be efficiently modulated in response to abiotic stress. However, the underlying mechanisms are not well understood. Here we report that ARABIDOPSIS THALIANA HOMEOBOX 17 (ATHB17), an Arabidopsis HD-Zip transcription factor, regulated the expression of a number of photosynthesis associated nuclear genes (PhANGs) involved in the light reaction and ATSIG5 in response to abiotic stress. ATHB17 was responsive to ABA and multiple stress treatments. ATHB17-overexpressing plants displayed enhanced stress tolerance, whereas its knockout mutant was more sensitive compared to the wild type. Through RNA-seq and quantitative real-time reverse transcription PCR (qRT-PCR) analysis, we found that ATHB17 did not affect the expression of many known stress-responsive marker genes. Interestingly, we found that ATHB17 down-regulated many PhANGs and could directly modulate the expression of several PhANGs by binding to their promoters. Moreover, we identified ATSIG5, encoding a plastid sigma factor, as one of the target genes of ATHB17. Loss of ATSIG5 reduced salt tolerance while overexpression of ATSIG5 enhanced salt tolerance, similar to that of ATHB17. ATHB17 can positively modulate the expression of many plastid encoded genes (PEGs) through regulation of ATSIG5. Taken together, our results suggest that ATHB17 may play an important role in protecting plants by adjusting expression of PhANGs and PEGs in response to abiotic stresses.

Highlights

Abiotic stresses such as salinity, drought, high light and unfavorable temperatures, adversely affect the growth and development of plants
There was only weak expression in other organs, such as rosette leaf (Fig. 1A-h), cauline leaf (Fig. 1A-i), flower and young silique (Fig. 1A-j), and mature silique (Fig. 1A-l). These results were confirmed by quantitative real-time reverse transcription PCR analysis shown in Fig. 1B, implying a potential function of ARABIDOPSIS THALIANA HOMEOBOX 17 (ATHB17) in roots
GATA-type transcription factors (TFs) GNC and CGA1 were reported to modulate the expression of chloroplast protein genes genomes uncoupled 4 (GUN4) and HEMA145

Summary

Introduction

Abiotic stresses such as salinity, drought, high light and unfavorable temperatures, adversely affect the growth and development of plants. Among the six sigma factors in Arabidopsis, only ATSIG5 expression is stress inducible and phylogenetically specific[23,24,25] It is induced by high light, low temperature, high salt and osmotic stress[17], as well as blue light[23]. ATSIG5 regulates the repair capacity from injury to the PS II reaction center by salt stress It does this by determining the promoter recognition specificity of PEP in plastid gene expression that activates psbD from the blue-light responsive promoter (BLRP)[9,27]. ATSIG5 regulates chloroplast psbD and psbA coding for the PS II core proteins D1 and D2 in response to light quality and intensity, and combines extrinsic and intrinsic signals important for adjusting nuclear and plastid gene transcription in light acclimation processes[28]

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Conclusion