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

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.

The Bcl-2-associated athanogene gene family in tobacco (Nicotiana tabacum) and the function of NtBAG5 in leaf senescence

“…Leaf senescence is a common process during plant growth and development and is regulated by variety of intrinsic factors, such as cell death, hormones, physiological and biochemical metabolism, senescencerelated gene regulation, and environmental factors (Jahan et al, 2021). Leaf senescence is usually accompanied with a visible color change from green to yellow or brown (Koyama, 2018).…”

“…Leaf senescence is usually accompanied with a visible color change from green to yellow or brown (Koyama, 2018). The internal structure of the leaf undergoes significant changes during senescence, manifested by an abnormal chloroplast structure and decreased in chlorophyll content (Jahan et al, 2021). Decreased of nucleic acid and protein contents and cytoprotective enzyme activity as well as enhanced membrane lipid peroxidation are also observed during plant leaf senescence.…”

BAG9 Confers Thermotolerance by Regulating Cellular Redox Homeostasis and the Stability of Heat Shock Proteins in Solanum lycopersicum

“…BAG5b (Solyc10g084170, namely BAG9 ) in leaves was activated by various adversity stimuli (extreme temperatures, salinity, and UV light) as well as treatment with phytohormones. Specifically, it improved the resistance to dark-induced leaf senescence by eliminating ROS and downgrading genes associated with leaf senescence [ 34 ].…”

“…For inhibiting senescence, the signal complex calmodulin-like motif (CaM)/AtBAG5/heat shock cognate 70 (Hsc70) upregulated a high level of Ca 2+ in mitochondria to inhibit senescence [ 33 ]. Likewise in tomato, BAG2 and BAG5b improved the resistance to dark-induced leaf senescence [ 34 ]. Various abiotic stresses induced AtBAG4 and regulated ion channels and stomatal motion by interacting with and adjusting KAT1 [ 35 , 36 ].…”

A Novel Senescence-Specific Gene (ZmSAG39) Negatively Regulates Darkness and Drought Responses in Maize

“…The tubes were placed in a 4 • C refrigerator in the dark for 24 h. The supernatant collected after extraction was the chlorophyll extract. Then, the chlorophyll concentrations were determined by detecting the absorbance at 665 nm and 649 nm using a UV2400 UV/VIS spectrophotometer (Soptpo, Shanghai, China) as previously described [55].…”