Mutual Promotion of LAP2 and CAT2 Synergistically Regulates Plant Salt and Osmotic Stress Tolerance.

Yu Zhang,Lin-Feng Wang,Wen-Cheng Liu,Ting-Ting Li

doi:10.3389/fpls.2021.672672

Yu Zhang, Lin-Feng Wang + Show 2 more

Open Access

https://doi.org/10.3389/fpls.2021.672672

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Abstract

Almost all abiotic stresses induce reactive oxygen species (ROS) overaccumulation, causing oxidative damages to plant cells. Catalase (CAT) plays a vital role in plant oxidative stress tolerance by scavenging stress-induced excess H2O2; thus, the identification of factors regulating catalase function will shed light on the underlying regulatory mechanisms. Here, we identified leucine aminopeptidase 2 (LAP2) as a novel CAT2-interacting protein and showed a mutual promotion effect of the two proteins in plant stress responses. LAP2 has a physical interaction with CAT2 in plant cells. The loss-of-function mutant of LAP2, lap2-3, is hypersensitive to salt or osmotic stress with increased ROS accumulation and malondialdehyde content and decreased catalase activity. The lap2-3 mutant has less CAT2 protein levels as CAT2 protein stability is impaired in the mutant. Scavenging excess ROS by glutathione or overexpressing CAT2 in the lap2-3 mutant recovers its hypersensitive phenotype to salt or osmotic stress. Further study showed that CAT2 promotes LAP2 hydrolysis activity with leucine-4-methylcoumaryl-7-amides as a substrate in vivo and in vitro, and thus, similar to the lap2-3 mutant, the cat2-1 mutant also has lower γ-aminobutyric acid content than the wild type. Together, our study reveals mutual promotion effects of CAT2 and LAP2 in conferring plant salt and osmotic stress tolerance.

Highlights

Soil salinity and water deficit are abiotic stresses that severely affect crop growth, quantity, and quality, causing enormous economic losses and serious food insecurity worldwide (Yang and Guo, 2018; Yu et al, 2020)
CAT2 plays a vital role in plant salt and drought stress tolerance by scavenging stress-induced H2O2; identification of factors regulating CAT2 function will shed light on the mechanisms underlying plant responses to high salinity or drought-induced oxidative stress
GFP-tagged leucine aminopeptidase 2 (LAP2) and Flag-tagged CAT2 were transiently co-expressed in N. benthamiana leaves, and CAT2Flag could be immunoprecipitated using anti-GFP antibody, indicating that CAT2 and LAP2 form a complex in plant cells (Figure 1B)

Summary

Introduction

Soil salinity and water deficit are abiotic stresses that severely affect crop growth, quantity, and quality, causing enormous economic losses and serious food insecurity worldwide (Yang and Guo, 2018; Yu et al, 2020) Due to their sessile lifestyle, plants usually cannot avoid high salinity- or drought-induced injuries by directly changing their location; plants have developed sophisticated adaptive mechanisms to respond to these stresses so as to survive and reproduce themselves (Li et al, 2015). Reactive oxygen species-scavenging enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase, peroxiredoxin, and non-enzymatic small molecules contribute to maintain ROS homeostasis by removing stress-induced excess ROS in plant cells (Hu et al, 2010; Sanchez-McSweeney et al, 2021) Among these ROS-scavenging enzymes, CAT plays a vital role in plant tolerance to high salinity and drought. A loss-of-function mutant of CAT3 with higher H2O2 accumulation in the leaves is severely sensitive to water deficit, while its overexpression transgenic plants are more tolerant than the wild-type plants when challenged with drought stress (Zou et al, 2015)

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