Characterization of SlBAG Genes from Solanum lycopersicum and Its Function in Response to Dark-Induced Leaf Senescence.

Mingming He,Jin Sun,Shirong Guo,Sheng Shu,Yu Wang,Mohammad Shah Jahan,Weikang Liu,Abdul Raziq

doi:10.3390/plants10050947

Abstract

The Bcl-2-associated athanogene (BAG) family is a group of evolutionarily conserved cochaperones involved in diverse cellular functions. Here, ten putative SlBAG genes were identified in tomato. SlBAG2 and SlBAG5b have the same gene structure and conserved domains, along with highly similar identity to their homologs in Arabidopsis thaliana, Oryza sativa, and Triticum aestivum. The qPCR data showed that BAG2 and BAG5b were highly expressed in stems and flowers. Moreover, both genes were differentially expressed under diverse abiotic stimuli, including cold stress, heat stress, salt treatment, and UV irradiation, and treatments with phytohormones, namely, ABA, SA, MeJA, and ETH. Subcellular localization showed that SlBAG2 and SlBAG5b were located in the cell membrane and nucleus. To elucidate the functions in leaf senescence of BAG2 and BAG5b, the full-length CDSs of BAG2 and BAG5b were cloned, and transgenic tomatoes were developed. Compared with WT plants, those overexpressing BAG2 and BAG5b had significantly increased chlorophyll contents, chlorophyll fluorescence parameters and photosynthetic rates but obviously decreased ROS levels, chlorophyll degradation and leaf senescence related gene expression under dark stress. Conclusively, overexpression SlBAG2 and SlBAG5b could improve the tolerance of tomato leaves to dark stress and delay leaf senescence.

Highlights

Leaf senescence is a fine regulatory mechanism caused by multiple internal factors, such as cell death, plant hormones, nutrient deficiency, senescence related genes, and environmental factors, such as drought, high temperature, salinity, weak light and darkness, and so on [1]
According to the previous names used in NCBI, the tomato Bcl-2-associated athanogene (BAG) family genes were named SlBAG1, SlBAG2, SlBAG3a, SlBAG3c, SlBAG4a, SlBAG4b, SlBAG5a, SlBAG5b, SlBAG6, and SlBAG7
It was noticed that the expression level of BAG2 in each organ was far higher than that of BAG5b, which implicated that the BAG2 played a dominant role in tomato plants. Both BAG genes were highly expressed in flowers and stems (Figure 6). These results show that BAG2 and BAG5b both perform an important role in plant development, and will guide our future work to figure out whether they play a critical role in flower and stem development

Summary

Introduction

Leaf senescence is a fine regulatory mechanism caused by multiple internal factors, such as cell death, plant hormones, nutrient deficiency, senescence related genes, and environmental factors, such as drought, high temperature, salinity, weak light and darkness, and so on [1]. Transcriptions of chlorophyll catabolism genes are directly relevant to the severity of environmental factors-induced leaf senescence in plants [6,7]. Another characteristic of leaf senescence is excessive accumulation of reactive oxygen species (ROS) [8,9], ROS homeostasis, and redox states regulated growth or senescence related cell death. Leaf senescence induced by darkness is the most effective method to study senescence [10,11]

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Results

Discussion

Conclusion