The molecular chaperone binding protein BiP prevents leaf dehydration-induced cellular homeostasis disruption.
BiP overexpression improves leaf water relations during droughts and delays drought-induced leaf senescence. However, whether BiP controls cellular homeostasis under drought conditions or simply delays dehydration-induced leaf senescence as the primary cause for water stress tolerance remains to be determined. To address this issue, we examined the drought-induced transcriptomes of BiP-overexpressing lines and wild-type (WT) lines under similar leaf water potential (ψw) values. In the WT leaves, a ψw reduction of -1.0 resulted in 1339 up-regulated and 2710 down-regulated genes; in the BiP-overexpressing line 35S::BiP-4, only 334 and 420 genes were induced and repressed, respectively, at a similar leaf ψw = -1.0 MPa. This level of leaf dehydration was low enough to induce a repertory of typical drought-responsive genes in WT leaves but not in 35S::BiP-4 dehydrated leaves. The responders included hormone-related genes, functional and regulatory genes involved in drought protection and senescence-associated genes. The number of differentially expressed genes in the 35S::BiP-4 line approached the wild type number at a leaf ψw = -1.6 MPa. However, N-rich protein (NRP)- mediated cell death signaling genes and unfolded protein response (UPR) genes were induced to a much lower extent in the 35S::BiP-4 line than in the WT even at ψw = -1.6 MPa. The heatmaps for UPR, ERAD (ER-associated degradation protein system), drought-responsive and cell death-associated genes revealed that the leaf transcriptome of 35S::BiP-4 at ψw = -1.0 MPa clustered together with the transcriptome of well-watered leaves and they diverged considerably from the drought-induced transcriptome of the WT (ψw = -1.0, -1.7 and -2.0 MPa) and 35S::BiP-4 leaves at ψw = -1.6 MPa. Taken together, our data revealed that BiP-overexpressing lines requires a much higher level of stress (ψw = -1.6 MPa) to respond to drought than that of WT (ψw = -1.0). Therefore, BiP overexpression maintains cellular homeostasis under water stress conditions and thus ameliorates endogenous osmotic stress.
National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil ; Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Humberto H
HH
Carvalho
National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil ; Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Otávio J B
OJ
Brustolini
Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Maiana R
MR
Pimenta
National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil ; Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Giselle C
GC
Mendes
National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil ; Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Bianca C
BC
Gouveia
National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil ; Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Priscila A
PA
Silva
Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
José Cleydson F
JC
Silva
National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Clenilso S
CS
Mota
Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Juliana R L
JR
Soares-Ramos
National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG, Brazil ; Departamento de Bioquímica e Biologia Molecular/Bioagro, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
Elizabeth P B
EP
Fontes
D000222:Adaptation, Physiological; D003890:Desiccation; D055864:Droughts; D000091342:Endoplasmic Reticulum Chaperone BiP; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006706:Homeostasis / Q000235:genetics*; D058977:Molecular Sequence Annotation; D018515:Plant Leaves / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D013025:Glycine max / Q000235:genetics* / Q000378:metabolism; D013312:Stress, Physiological / Q000235:genetics; D059467:Transcriptome
D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D010940:Plant Proteins