AcoMYB4, an Ananas comosus L. MYB Transcription Factor, Functions in Osmotic Stress through Negative Regulation of ABA Signaling.

Xiaoping Niu,Lanxin Li,Yuan Qin,Bello Hassan Jakada,Qing He,Mengnan Chai,Huihuang Chen,Youmei Huang,Linyi Lai,Liping Liu

doi:10.3390/ijms21165727

Abstract

Drought and salt stress are the main environmental cues affecting the survival, development, distribution, and yield of crops worldwide. MYB transcription factors play a crucial role in plants’ biological processes, but the function of pineapple MYB genes is still obscure. In this study, one of the pineapple MYB transcription factors, AcoMYB4, was isolated and characterized. The results showed that AcoMYB4 is localized in the cell nucleus, and its expression is induced by low temperature, drought, salt stress, and hormonal stimulation, especially by abscisic acid (ABA). Overexpression of AcoMYB4 in rice and Arabidopsis enhanced plant sensitivity to osmotic stress; it led to an increase in the number stomata on leaf surfaces and lower germination rate under salt and drought stress. Furthermore, in AcoMYB4 OE lines, the membrane oxidation index, free proline, and soluble sugar contents were decreased. In contrast, electrolyte leakage and malondialdehyde (MDA) content increased significantly due to membrane injury, indicating higher sensitivity to drought and salinity stresses. Besides the above, both the expression level and activities of several antioxidant enzymes were decreased, indicating lower antioxidant activity in AcoMYB4 transgenic plants. Moreover, under osmotic stress, overexpression of AcoMYB4 inhibited ABA biosynthesis through a decrease in the transcription of genes responsible for ABA synthesis (ABA1 and ABA2) and ABA signal transduction factor ABI5. These results suggest that AcoMYB4 negatively regulates osmotic stress by attenuating cellular ABA biosynthesis and signal transduction pathways.

Highlights

As sessile organisms, plants cannot escape adverse environmental conditions like animals can
Our results showed that AcoMYB4 responded positively to cold, drought, salt, ethephon (Eth), salicylic acid (SA), and abscisic acid (ABA) (Figure 2A–F)
AcoMYB4 possessed the signature motifs defining a typical R2R3-type MYB, and multiple alignments revealed that AcoMYB4 shared high identity with AtMYB4, AtMYB7, and AtMYB32, indicating that AcoMYB4 is a putative homologue of pineapple

Summary

Introduction

Plants cannot escape adverse environmental conditions like animals can. Biotic and abiotic stresses such as salt stress, drought, heavy metal ion toxicity, and extreme temperature affect plant growth and development and productivity and geographical distribution. To cope with these stresses, plants have evolved elaborate mechanisms ranging from the perception of various stress signals to the modification of physiological and biochemical responses [1]. Plant cells are undergoing numerous changes by regulating a multitude of stress-responsive genes, which can be mainly classified into effectors and regulators based on their functional products [2]. Transcription factors play a dominant role in orchestrating stress signals and functional gene expression, shielding plants from damage resulting from stress [3]. Genetic engineering of stress-related transcription factors has been proposed to be a promising strategy to improve the stress tolerance of crops for the sustainable development of agricultural production and planting environment [4]

Methods

Results

Conclusion