PpSARK Regulates Moss Senescence and Salt Tolerance through ABA Related Pathway.

Ping Li,Li Liu,Hong Yang,Gaojing Liu,Chuanhong Li,Wenzhang Ma,Heqiang Huo,Jianfang He

doi:10.3390/ijms19092609

Abstract

Senescence-associated receptor-like kinase (SARK) family members in Arabidopsis, soybean, and rice are known to be positive regulators of leaf senescence. In the meantime, SARKs are extensively involved in stress response. However, their function and underlying molecular mechanism in stress responses in moss are not well known. Here, we investigated functional roles of SARK isolated from Physcomitrella patens (PpSARK) in salt stress response and senescence. PpSARK transcripts significantly accumulated under NaCl and abscisic acid (ABA) treatments, with higher expression in the moss gametophyte stage. Insertional gain-of-function mutants of PpSARK (PpSARKg) were more tolerant to salt stress and ABA than wild type (WT), whereas senescence of mutants was delayed during the protonema stage. Expression of stress-responsive genes in the ABA related pathway, such as PpABI3, PpABI5, PpPP2C, and PpLEA were significantly higher in PpSARKg and WT under salt stress conditions, suggesting that PpSARK might positively regulate salt tolerance via an ABA-related pathway. Endogenous ABA contents also increased 3-fold under salt stress conditions. These results indicate that PpSARK functions as a positive regulator in salt stress responses, while possibly functioning as a negative regulator in senescence in moss.

Highlights

Leaf senescence is the final stage of leaf developmental processes that are influenced by both internal genetic factors and external environmental cues such as temperature [1]
To explore the function of PpSARK (Pp3c22_12040), we firstly investigated the expression pattern of PpSARK in wild-type moss and identified that PpSARK was induced by gametophore development, abscisic acid (ABA), and salt stress treatment (Figure 1)
The expression of PpSARK increased 4-fold under ABA, and 3-fold under salt treatment in gametophores. This result suggests that PpSARK is a senescence-associated gene, which mainly functions in the gametophores of moss and may be induced by ABA and NaCl

Summary

Introduction

Leaf senescence is the final stage of leaf developmental processes that are influenced by both internal genetic factors and external environmental cues such as temperature [1]. Overexpression of ABA receptor PYL9 driven by the RD29A promoter resulted in better drought tolerance and accelerated leaf senescence. The PYL9 promoter, ABA, induced leaf senescence and drought tolerance via inhibiting PP2Cs and activating SnRK2s [2]. Senescence-associated receptor-like kinases (SARKs) are widely reported to be involved in abiotic and biotic stress resistance [9]. Crosslinks between ROS and ABA (abscisic acid)-dependent signaling, together with ion homeostasis and the sumoylation pathways in plant salt and drought tolerance were established [12,13,14]. RNA sequencing (RNA-seq) and small RNA sequencing (sRNA-seq) data of citrus roots confirmed that signal transduction, hormone-mediated signaling pathways, ROS metabolic processes, and transcription factors were involved in dehydration and/or salt treatment [15]. Most of the progress in understanding the crosstalk of senescence and stress resistance comes from the model dicot plant Arabidopsis thaliana, while limited information is known about moss mechanisms [16]

Methods

Results

Conclusion