Abstract
Maintaining reactive oxygen species (ROS) homeostasis plays a central role in plants, and is also critical for plant root development. Threshold levels of ROS act as signals for elongation and differentiation of root cells. The protein phosphatase LIKE SEX FOUR2 (LSF2) has been reported to regulate starch metabolism in Arabidopsis, but little is known about the mechanism how LSF2 affect ROS homeostasis. Here, we identified that LSF2 function as a component modulating ROS homeostasis in response to oxidative stress and, thus regulate root development. Compared with wild type Arabidopsis, lsf2-1 mutant exhibited reduced rates of superoxide generation and higher levels of hydrogen peroxide upon oxidative stress treatments. The activities of several antioxidant enzymes, including superoxide dismutase, catalase, and ascorbate peroxidase, were also affected in lsf2-1 mutant under these oxidative stress conditions. Consequently, lsf2-1 mutant exhibited the reduced root growth but less inhibition of root hair formation compared to wild type Arabidopsis plants. Importantly, protein phosphatase LSF2 interacted with mitogen-activated protein kinase 8 (MPK8), a known component of ROS homeostasis pathways in the cytoplasm. These findings indicated the novel function of LSF2 that controls ROS homeostasis to regulate root development.
Highlights
SOD (Cu/Zn-SOD), catalyze the dismutation of O2− to H2O2 and molecular oxygen (O2)[9]
Arabidopsis UPBEAT1 (UPB1) controls the balance between O2− and H2O2 by repressing peroxidases; upb[1] mutant plants contain higher O2− levels and lower H2O2 levels in the root tip compared with the wild type plants, suggesting that Reactive oxygen species (ROS) homeostasis is altered in these plants, leading to changes in root growth and development[11]
The transcriptional expression of ROOT HAIR DEFECTIVE6 (RHD6) was very significantly higher in lsf[] than in Col-0 under oxidative stress conditions (Fig. 4d). These results indicate that deficiency of LIKE SEX FOUR2 (LSF2) in Arabidopsis results in less inhibition of root hair development, as well as less inhibition of RHD6 expression, under oxidative stress conditions compared with normal growth condition (Fig. 4d, untreated)
Summary
SOD (Cu/Zn-SOD), catalyze the dismutation of O2− to H2O2 and molecular oxygen (O2)[9]. CAT is the key enzyme that scavenges H2O2, with a high reaction rate but low affinity for H2O210. In Arabidopsis, protein phosphatases play key roles in regulating cellular activities and often affect ROS homeostasis, especially in response to environmental stimuli[15,16,17]. SEX4 is a major phosphatase that binds to starch granules, and is regulated by redox[18]. No study has proved that LSF2 activity is controlled by redox in plants[21]. In this present study, for the first time, we identify that LSF2 plays a role in ROS homeostasis to regulate root growth and root hair development in Arabidopsis
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