The nuclear transporter SAD2 plays a role in calcium‐ and H₂O₂‐mediated cell death in Arabidopsis

Abstract

Summary In response to pathogens, plant cells exhibit a rapid increase in the intracellular calcium concentration and a burst of reactive oxygen species (ROS). The cytosolic increase in Ca2+ and the accumulation of ROS are critical for inducing programmed cell death (PCD), but the molecular mechanism is not fully understood. We screened an Arabidopsis mutant, sad2‐5, which harbours a T‐DNA insertion in the 18th exon of the importin beta‐like gene, SAD2. The H2O2‐induced increase in the [Ca2+]cyt of the sad2‐5 mutant was greater than that of the wild type, and the sad2‐5 mutant showed clear cell death phenotypes and abnormal H2O2 accumulation under fumonisin‐B1 (FB1) treatment. CaCl2 could enhance the FB1‐induced cell death of the sad2‐5 mutant, whereas lanthanum chloride (LaCl3), a broad‐spectrum calcium channel blocker, could restore the FB1‐induced PCD phenotype of sad2‐5. The sad2‐5 fbr11‐1 double mutant exhibited the same FB1‐insensitive phenotype as fbr11‐1, which plays a critical role in novo sphingolipid synthesis, indicating that SAD2 works downstream of FBR11. These results suggest the important role of nuclear transporters in calcium‐ and ROS‐mediated PCD response as well as provide an important theoretical basis for further analysis of the molecular mechanism of SAD2 function in PCD and for improvement of the resistance of crops to adverse environments.

Fumonisin B1: A Tool for Exploring the Multiple Functions of Sphingolipids in Plants

“…The FB1 sensitivity of sad2-5 is partially dependent on Ca 2+ signaling (Zheng et al, 2019). SAD2-mediated Ca 2+ and ROS signaling appear to function downstream of LCB, since the sad2-5 fbr11-1 double mutant exhibited the same FB1-insensitive phenotype as fbr11-1 (Zheng et al, 2019). In fact, many signaling pathways involved in regulating FB1-induced cell death are associated with ROS.…”

“…The cytosolic increase in Ca 2+ levels and the accumulation of ROS are critical for inducing PCD. The disruption of Arabidopsis super sensitive to aba and drought 2 (SAD2) (an importin beta-like gene) enhanced H 2 O 2 accumulation and cell death in the sad2-5 mutant under FB1 treatment (Zheng et al, 2019). The FB1 sensitivity of sad2-5 is partially dependent on Ca 2+ signaling (Zheng et al, 2019).…”

“…The disruption of Arabidopsis super sensitive to aba and drought 2 (SAD2) (an importin beta-like gene) enhanced H 2 O 2 accumulation and cell death in the sad2-5 mutant under FB1 treatment (Zheng et al, 2019). The FB1 sensitivity of sad2-5 is partially dependent on Ca 2+ signaling (Zheng et al, 2019). SAD2-mediated Ca 2+ and ROS signaling appear to function downstream of LCB, since the sad2-5 fbr11-1 double mutant exhibited the same FB1-insensitive phenotype as fbr11-1 (Zheng et al, 2019).…”

Calcium Signaling in Plant Programmed Cell Death

“…In Arabidopsis , a mutation in the nuclear transporter SAD2 (sensitive to ABA and drought 2) is responsible for H 2 O 2 -induced cytosolic Ca 2+ increase. Further research showed that SAD2 works downstream of FBR11 (fumonisin B1-resistant 11) and plays a role in Ca 2+ - and H 2 O 2 -mediated cell death [ 6 ]. Recently, H 2 O 2 sensor LRR receptor kinase HPCA1 (hydrogen peroxide-induced Ca 2+ increase 1) has been demonstrated to mediate H 2 O 2 -induced activation of Ca 2+ channels in guard cells [ 152 ].…”

“…It is reported that calcium (Ca 2+ ), a universal second messenger, is critical for PCD in plants [ 6 ]. Transient changes in cytosolic Ca 2+ level are rapidly induced by diverse stimuli in plants [ 7 , 8 ].…”