Protein trafficking during plant innate immunity

Plants have evolved a sophisticated immune system to fight against pathogenic microbes. Upon detection of pathogen invasion by immune receptors, the immune system is turned on, resulting in production of antimicrobial molecules including pathogenesis-related（PR） proteins.Conceivably, an efficient immune response depends on the capacity of the plant cell＇s protein/membrane trafficking network to deploy the right defense-associated molecules in the right place at the right time. Recent research in this area shows that while the abundance of cell surface immune receptors is regulated by endocytosis, many intracellular immune receptors, when activated, are partitioned between the cytoplasm and the nucleus for induction of defense genes and activation of programmed cell death, respectively. Vesicle transport is an essential process for secretion of PR proteins to the apoplastic space and targeting of defense-related proteins to the plasma membrane or other endomembrane compartments. In this review, we discuss the various aspects of protein trafficking during plant immunity, with a focus on the immunity proteins on the move and the major components of the trafficking machineries engaged.

Nuclear translocation of OsMFT1 that is impeded by OsFTIP1 promotes drought toleranee in rice

Drought is the leading environmental threat affecting crop productivity,and plants have evolved a series of mechanisms to adapt to drought stress.The FT-interacting proteins(FTIPs)and phosphatidylethanola mine.binding proteins(PEBPs)play key roles in developmental processes,whereas their roles in the regulation of stress response are still largely unknown.Here,we report that OsFTIP1 negatively regulates drought response in rice.We showed that OsFTIP1 interacts with rice MOTHER OF FT AND TFL1(OsMFT1),a PEBP that promotes rice tolerance to drought treatment.Further studies discovered that OsMFT1 interacts with two key drought-related transcription factors,OsbZIP66 and OsMYB26,regulating their binding capacity on drought-related genes and thereby enhancing drought toleranee in rice.Interestingly,we found that OsFTIP1 impedes the nucleocytoplasmic translocation of OsMFT1,implying that dynamic modulation of drought-responsive genes by the OsMFT1-OsMYB26 and OsMFT1-OsbZIP66 complexes is integral to OsFTIP1-modulated nuclear accumulation of OsMFT1.Our findings also suggest that OsMFT1 might act as a hitherto unknown nucleocytoplasmic trafficking signal that regulates drought tolerance in rice in response to environmental signals.

The OsFTIP6-OsHB22-OsMYBR57 module regulates drought response in rice

Plants have evolved a sophisticated set of mechanisms to adapt to drought stress.Transcription factors play crucial roles in plant responses to various environmental stimuli by modulating the expression of numerous stress-responsive genes.However,how the crosstalk between different transcription factor families orchestrates initiation of the key transcriptional network and the role of posttranscriptional modification of transcription factors,especially in cellular localization/trafficking in response to stress in rice,remain still largely unknown.In this study,we isolated an Osmybr57 mutant that displays a drought-sensitive phenotype through a genetic screen for drought stress sensitivity.We found that OsMYBR57,an MYB-related protein,directly regulates the expression of several key drought-related OsbZ/Ps in response to drought treatment.Further studies revealed that OsMYBR57 interacts with a homeodomain transcription factor,OsHB22,which also plays a positive role in drought signaling.We further demonstrate that OsFTIP6 interacts with OsHB22 and promotes the nucleocytoplasmic translocation of OsHB22 into the nucleus,where OsHB22 cooperates with OsMYBR57 to regulate the expression of drought-responsive genes.Our findings have revealed a mechanistic framework underlying the OsFTIP6-0sHB22-0sMYBR57 module-mediated regulation of drought response in rice.The OsFTIP6-mediated OsHB22 nucleocytoplasmic shuttling and OsMYBR57-0sHB22 regulation of OsbZIP transcription ensure precise control of expression of OsLEA3 and Rab21,and thereby regulate the response to water deficiency in rice.