OsKASI-2 is required for the regulation of unsaturation levels of membrane lipids and chilling tolerance in rice.

Chilling stress has seriously limited the global production and geographical distribution of rice. However, the molecular mechanisms associated with plant responses to chilling stress are less known. In this study, we revealed a member of ß-ketoacyl-ACP synthase I family (KASI), OsKASI-2 which confers chilling tolerance in rice. OsKASI-2 encodes a chloroplast-localized KASI enzyme mainly expressed in the leaves and anthers of rice and strongly induced by chilling stress. Disruption of OsKASI-2 led to decreased KAS enzymatic activity and the levels of unsaturated fatty acids, which impairs degree of unsaturation of membrane lipids, thus increased sensitivity to chilling stress in rice. However, the overexpression of OsKASI-2 significantly improved the chilling tolerance ability in rice. In addition, OsKASI-2 may regulate ROS metabolism in response to chilling stress. Natural variation of OsKASI-2 might result in difference in chilling tolerance between indica and japonica accessions, and Hap1 of OsKASI-2 confers chilling tolerance in rice. Taken together, we suggest OsKASI-2 is critical for regulating degree of unsaturation of membrane lipids and ROS accumulation for maintenance of membrane structural homeostasis under chilling stress, and provide a potential target gene for improving chilling tolerance of rice.

Jacalin-related lectin 45 (OsJRL45) isolated from 'sea rice 86' enhances rice salt tolerance at the seedling and reproductive stages.

BACKGROUND: Rice (Oryza sativa L.) is one of the most widely cultivated grain crops in the world that meets the caloric needs of more than half the world's population. Salt stress seriously affects rice production and threatens food security. Therefore, mining salt tolerance genes in salt-tolerant germplasm and elucidating their molecular mechanisms in rice are necessary for the breeding of salt tolerant cultivars. RESULTS: In this study, a salt stress-responsive jacalin-related lectin (JRL) family gene, OsJRL45, was identified in the salt-tolerant rice variety 'sea rice 86' (SR86). OsJRL45 showed high expression level in leaves, and the corresponding protein mainly localized to the endoplasmic reticulum. The knockout mutant and overexpression lines of OsJRL45 revealed that OsJRL45 positively regulates the salt tolerance of rice plants at all growth stages. Compared with the wild type (WT), the OsJRL45 overexpression lines showed greater salt tolerance at the reproductive stage, and significantly higher seed setting rate and 1,000-grain weight. Moreover, OsJRL45 expression significantly improved the salt-resistant ability and yield of a salt-sensitive indica cultivar, L6-23. Furthermore, OsJRL45 enhanced the antioxidant capacity of rice plants and facilitated the maintenance of Na+-K+ homeostasis under salt stress conditions. Five proteins associated with OsJRL45 were screened by transcriptome and interaction network analysis, of which one, the transmembrane transporter Os10g0210500 affects the salt tolerance of rice by regulating ion transport-, salt stress-, and hormone-responsive proteins. CONCLUSIONS: The OsJRL45 gene isolated from SR86 positively regulated the salt tolerance of rice plants at all growth stages, and significantly increased the yield of salt-sensitive rice cultivar under NaCl treatment. OsJRL45 increased the activity of antioxidant enzyme of rice and regulated Na+/K+ dynamic equilibrium under salinity conditions. Our data suggest that OsJRL45 may improve the salt tolerance of rice by mediating the expression of ion transport-, salt stress response-, and hormone response-related genes.

OsJRL40, a Jacalin-Related Lectin Gene, Promotes Salt Stress Tolerance in Rice.

High salinity is a major stress factor affecting the quality and productivity of rice (Oryza sativa L.). Although numerous salt tolerance-related genes have been identified in rice, their molecular mechanisms remain unknown. Here, we report that OsJRL40, a jacalin-related lectin gene, confers remarkable salt tolerance in rice. The loss of function of OsJRL40 increased sensitivity to salt stress in rice, whereas its overexpression enhanced salt tolerance at the seedling stage and during reproductive growth. ß-glucuronidase (GUS) reporter assays indicated that OsJRL40 is expressed to higher levels in roots and internodes than in other tissues, and subcellular localization analysis revealed that the OsJRL40 protein localizes to the cytoplasm. Further molecular analyses showed that OsJRL40 enhances antioxidant enzyme activities and regulates Na+-K+ homeostasis under salt stress. RNA-seq analysis revealed that OsJRL40 regulates salt tolerance in rice by controlling the expression of genes encoding Na+/K+ transporters, salt-responsive transcription factors, and other salt response-related proteins. Overall, this study provides a scientific basis for an in-depth investigation of the salt tolerance mechanism in rice and could guide the breeding of salt-tolerant rice cultivars.

SiNCED1, a 9-cis-epoxycarotenoid dioxygenase gene in Setaria italica, is involved in drought tolerance and seed germination in transgenic Arabidopsis.

Foxtail millet (Setaria italica L.) is a vital cereal food crop with promising development and utilization potential because of its outstanding ability to resist drought stress. However, the molecular mechanisms underlying its drought stress resistance remain unclear. In this study, we aimed to elucidate the molecular function of a 9-cis-epoxycarotenoid dioxygenase gene, SiNCED1, in the drought stress response of foxtail millet. Expression pattern analysis showed that SiNCED1 expression was significantly induced by abscisic acid (ABA), osmotic stress, and salt stress. Furthermore, ectopic overexpression of SiNCED1 could enhance drought stress resistance by elevating endogenous ABA levels and promoting stomatal closure. Transcript analysis indicated that SiNCED1 modulated ABA-related stress responsive gene expression. In addition, we found that ectopic expression of SiNCED1 delayed seed germination under normal and abiotic stress conditions. Taken together, our results show that SiNCED1 plays a positive role in the drought tolerance and seed dormancy of foxtail millet by modulating ABA biosynthesis. In conclusion, this study revealed that SiNCED1 is an important candidate gene for the improvement of drought stress tolerance in foxtail millet and could be beneficial in the breeding and investigation of drought tolerance in other agronomic crops.

Identification of Salt Tolerance Related Candidate Genes in 'Sea Rice 86' at the Seedling and Reproductive Stages Using QTL-Seq and BSA-Seq.

Salt stress seriously affects plant growth and development and reduces the yield of rice. Therefore, the development of salt-tolerant high-yielding rice cultivars through quantitative trait locus (QTL) identification and bulked segregant analysis (BSA) is the main focus of molecular breeding projects. In this study, sea rice (SR86) showed greater salt tolerance than conventional rice. Under salt stress, the cell membrane and chlorophyll were more stable and the antioxidant enzyme activity was higher in SR86 than in conventional rice. Thirty extremely salt-tolerant plants and thirty extremely salt-sensitive plants were selected from the F2 progenies of SR86 × Nipponbare (Nip) and SR86 × 9311 crosses during the whole vegetative and reproductive growth period and mixed bulks were generated. Eleven salt tolerance related candidate genes were located using QTL-seq together with BSA. Real time quantitative PCR (RT-qPCR) analysis showed that LOC_Os04g03320.1 and BGIOSGA019540 were expressed at higher levels in the SR86 plants than in Nip and 9311 plants, suggesting that these genes are critical for the salt tolerance of SR86. The QTLs identified using this method could be effectively utilized in future salt tolerance breeding programs, providing important theoretical significance and application value for rice salt tolerance breeding.

bHLH57 confers chilling tolerance and grain yield improvement in rice.

Chilling stress has become a major limiting factor that reduces crop productivity worldwide. In this study, we identified a new gene bHLH57, whose product enhances chilling tolerance in rice at diverse developmental stages. bHLH57 was mainly expressed in leaves and anthers, and its protein was targeted to the nucleus. Overexpression of bHLH57 enhanced chilling tolerance by increasing trehalose synthesis, whereas its mutants by CRISPR/Cas9-mediated mutagenesis were more sensitive to chilling and had reduced trehalose. Meanwhile, bHLH57 may regulate ROS metabolism and CBFs/DREBs- dependent pathways in response to chilling stress. In addition, the overexpression of bHLH57 resulted in increased grain yield under normal and chilling conditions, however, the disruption of bHLH57 displayed decreased grain size and seed setting rate, thus reduced grain yield. Phylogenetic and nucleotide diversity analyses suggested that bHLH57 is relatively conserved in monocotyledons, and may be selected during indica populations adaptation. Taken together, we have identified a new bHLH regulator involved rice chilling tolerance and grain yield, and provide a potential target gene for improving chilling tolerance and grain yield of rice.

ABA biosynthesis gene OsNCED3 contributes to preharvest sprouting resistance and grain development in rice.

Preharvest sprouting (PHS) is an unfavorable trait in cereal crops and causes serious yield loss. However, the molecular mechanism underlying PHS remains largely elusive. Here, we identified a member of 9-cis-epoxycarotenoid dioxygenase family, OsNCED3, which regulates PHS and grain development in rice (Oryza sativa L.). OsNCED3 encodes a chloroplast-localized abscisic acid (ABA) biosynthetic enzyme highly expressed in the embryo of developing seeds. Disruption of OsNCED3 by CRISPR/Cas9-mediated mutagenesis led to a lower ABA and higher gibberellic acid (GA) levels (thus a skewed ABA/GA ratio) in the embryo, promoting embryos growth and breaking seed dormancy before seed maturity and harvest, thus decreased seed dormancy and enhanced PHS in rice. However, the overexpression of OsNCED3 enhanced PHS resistance by regulating proper ABA/GA ratio in the embryo. Intriguingly, the overexpression of OsNCED3 resulted in increased grain size and weight, whereas the disruption of OsNCED3 function decreased grain size and weight. Nucleotide diversity analyses suggested that OsNCED3 may be selected during japonica populations adaptation of seed dormancy and germination. Taken together, we have identified a new OsNCED regulator involved rice PHS and grain development, and provide a potential target gene for improving PHS resistance and grain development in rice.

Agrobacterium-Mediated High-Efficiency Genetic Transformation and Genome Editing of Chaling Common Wild Rice (Oryza rufipogon Griff.) Using Scutellum Tissue of Embryos in Mature Seeds.

Genetic transformation is an important strategy for revealing gene function, and it is used extensively in both functional genomics study and molecular breeding of rice. Demand for its application in wild Oryza species is rising for their extensive genetic diversity. However, genetic transformation of wild Oryza accessions with AA genome using calli induced from scutellum tissue of embryos in mature seeds has not been successfully established. In the present study, we used Chaling common wild rice (CLCWR) (Oryza rufipogon Griff.) with AA genome to successfully establish an Agrobacterium-mediated genetic transformation system based on scutellum tissue of embryos in mature seeds. The calli from embryos in mature seeds of CLCWR were easy to be induced and regenerated. The callus induction rate and texture were optimum under 2.5 mg/L 2,4-D. The optimal hormone combination used for regeneration was 2 mg/L ZT + 0.1 mg/L NAA. Studies on genetic transformation and genome editing showed that the transformation efficiency was 87-94%, the efficiency of single genome editing and multiplex genome editing were about 60-70% and 20-40%, respectively. Compared with Nipponbare (Nip), CLCWR had higher Hygromycin-resistant callus frequency and transformation efficiency. Taken together, our study establishes a highly efficient transformation system for common wild rice with AA genome and provides a good rice material for de novo domestication by genome editing in the future.

Rice Na+-Permeable Transporter OsHAK12 Mediates Shoots Na+ Exclusion in Response to Salt Stress.

Soil salinity has become a major stress factor that reduces crop productivity worldwide. Sodium (Na+) toxicity in a number of crop plants is tightly linked with shoot Na+ overaccumulation, thus Na+ exclusion from shoot is crucial for salt tolerance in crops. In this study, we identified a member of the high-affinity K+ transport family (HAK), OsHAK12, which mediates shoots Na+ exclusion in response to salt stress in rice. The Oshak12 mutants showed sensitivity to salt toxicity and accumulated more Na+ in the xylem sap, leading to excessive Na+ in the shoots and less Na+ in the roots. Unlike typical HAK family transporters that transport K+, OsHAK12 is a Na+-permeable plasma membrane transporter. In addition, OsHAK12 was strongly expressed in the root vascular tissues and induced by salt stress. These findings indicate that OsHAK12 mediates Na+ exclusion from shoot, possibly by retrieving Na+ from xylem vessel thereby reducing Na+ content in the shoots. These findings provide a unique function of a rice HAK family member and provide a potential target gene for improving salt tolerance of rice.

Rice Potassium Transporter OsHAK8 Mediates K+ Uptake and Translocation in Response to Low K+ Stress.

Potassium (K+) levels in the soil often limit plant growth and development. As a result, crop production largely relies on the heavy use of chemical fertilizers, presenting a challenging problem in sustainable agriculture. To breed crops with higher K+-use efficiency (KUE), we must learn how K+ is acquired from the soil by the root system and transported to the rest of the plant through K+ transporters. In this study, we identified the function of the rice K+ transporter OsHAK8, whose expression level is downregulated in response to low-K+ stress. When OsHAK8 was disrupted by CRISPR/Cas9-mediated mutagenesis, Oshak8 mutant plants showed stunted growth, especially under low-K+ conditions. Ion content analyses indicated that K+ uptake and root-to-shoot K+ transport were significantly impaired in Oshak8 mutants under low-K+ conditions. As the OsHAK8 gene was broadly expressed in different cell types in the roots and its protein was targeted to the plasma membrane, we propose that OsHAK8 serves as a major transporter for both uptake and root-to-shoot translocation in rice plants.

Association between sequence variants in cadmium-related genes and the cadmium accumulation trait in thermo-sensitive genic male sterile rice.

Although cultivation of hybrid rice varieties has been increasing, there are risks that high levels of cadmium (Cd) will accumulate in grain when such rice is grown in Cd-polluted environments. To produce Cd-safe hybrid rice, one practical approach is the generation of low Cd-accumulating parental lines. In two-line hybrid breeding, thermosensitive genic male sterile (TGMS) lines function as female parents to yield hybrid seeds. Recently, Cd accumulation-related genes have been identified; however, the effect of these genes on Cd accumulation in the grains of TGMS lines has yet to be reported. Here, 174 TGMS lines were selected for Cd accumulation phenotyping, and 30 TGMS lines, including 15 stable low-Cd and 15 high-Cd lines, were selected for single-nucleotide polymorphism (SNP) genotyping and association analysis. Association studies were conducted to identify the relationship between Cd accumulation and variable sites within seven candidate Cd-associated genes using logistic models. Nine sequence variant sites in four of the candidate genes were found to be significantly associated with Cd accumulation, two of which in OsNRAMP1 and OsNRAMP5 are low-Cd favorable variants, explaining 46.4% and 22.6% of the phenotypic variation, respectively. These loci could be developed as new molecular markers for identification of Cd accumulation characteristics and low-Cd marker-assisted breeding.

OsNCED5, a 9-cis-epoxycarotenoid dioxygenase gene, regulates salt and water stress tolerance and leaf senescence in rice.

9-cis-epoxycarotenoid dioxygenase (NCED) is a rate-limiting enzyme for abscisic acid (ABA) biosynthesis. However, the molecular mechanisms of NCED5 that modulate plant development and abiotic stress tolerance are still unclear, particular in rice. Here, we demonstrate that a rice NCED gene, OsNCED5, was expressed in all tissues we tested, and was induced by exposure to salt stress, water stress, and darkness. Mutational analysis showed that nced5 mutants reduced ABA level and decreased tolerance to salt and water stress and delayed leaf senescence. However, OsNCED5 overexpression increased ABA level, enhanced tolerance to the stresses, and accelerated leaf senescence. Transcript analysis showed that OsNCED5 regulated ABA-dependent abiotic stress and senescence-related gene expression. Additionally, ectopic expression of OsNCED5 tested in Arabidopsis thaliana altered plant size and leaf morphology and delayed seed germination and flowering time. Thus, OsNCED5 may regulate plant development and stress resistance through control of ABA biosynthesis. These findings contribute to our understanding of the molecular mechanisms by which NCED regulates plant development and responses to abiotic stress in different crop species.

The trehalose-6-phosphate synthase TPS5 negatively regulates ABA signaling in Arabidopsis thaliana.

KEY MESSAGE: The TPS5 negatively regulates ABA signaling by mediating ROS level and NR activity during seed germination and stomatal closure in Arabidopsis thaliana. Trehalose metabolism is important in plant growth and development and in abiotic stress response. Eleven TPS genes were identified in Arabidopsis, divided into Class I (TPS1-TPS4) and Class II (TPS5-TPS11). Although Class I has been shown to have TPS activity, the function of most members of Class II remains enigmatic. Here, we characterized the biological function of the trehalose-6-phosphate synthase TPS5 in ABA signaling in Arabidopsis. TPS5 expression was induced by ABA and abiotic stress, and expression in epidermal and guard cells was dramatically increased after ABA treatment. Loss-of-function analysis revealed that tps5 mutants (tps5-1 and tps5-cas9) are more sensitive to ABA during seed germination and ABA-mediated stomatal closure. Furthermore, the H2O2 level increased in the tps5-1 and tps5-cas9 mutants, which was consistent with the changes in the expression of RbohD and RbohF, key genes responsible for H2O2 production. Further, TPS5 knockout reduced the amounts of trehalose and other soluble carbohydrates as well as nitrate reductase (NR) activity. In vitro, trehalose and other soluble carbohydrates promoted NR activity, which was blocked by the tricarboxylic acid cycle inhibitor iodoacetic acid. Thus, this study identified that TPS5 functions as a negative regulator of ABA signaling and is involved in altering the trehalose content and NR activity.

A quantitative proteomic analysis of the molecular mechanism underlying fertility conversion in thermo-sensitive genetic male sterility line AnnongS-1.

BACKGROUND: Thermo-sensitive genetic male sterile (TGMS) lines have been widely used in two-line hybrid rice breeding. The two-line hybrids have increased rice yields substantially. However, the effect of environmental temperatures on the fertility conversion is still not fully clear. In this study, we performed a tandem mass tag (TMT)-based proteomic analysis on the anthers of the TGMS line AnnongS-1 grown under permissive (low) temperature (21 °C) and restrictive (high) temperature (> 26 °C) conditions in an attempt to explore the effect of temperature on the fertility of the male sterile line. RESULTS: After the AnnongS-1 plants were induced under either permissive or restrictive conditions, morphological observations and I2-KI staining confirmed that the pollen grains formed under high temperature conditions were abortive while those formed under low temperature developed normally. In comparison to the plants grown under permissive conditions, the restrictive high-temperature conditions led to the differential accumulation of 89 proteins in the anthers, of which 46 were increased in abundance and 43 were decreased in abundance. Most of the subcellular compartments of the anther cells had one or more proteins that had been differentially accumulated, with the cytoplasm and chloroplast having the greatest accumulations. More than 40% of the differentially abundant proteins (DAPs) were enzymes involved in photosynthesis, energy metabolism, biosynthesis and catabolism of cellular components, metabolic regulation, defense and stress, etc. The DAPs related to protein metabolism accounted for the largest proportion (21.35%), followed by those related to defense and stress (12.36%), metabolic regulation (10.11%) and carbohydrate metabolism (8.99%), indicating that such biological processes in anther cells were more susceptible to high temperature stress. CONCLUSIONS: The restrictive temperature induction caused fertility-sterility conversion in the TGMS line AnnongS-1 mainly by adversely affecting the metabolism of protein, carbohydrate and energy, and decreasing the abundances of important proteins closely related to defense and stress, thereby impeding the growth and development of the pollen and weakening the overall defense and ability to endure stress of AnnongS-1. These data are helpful for deepening our understanding of the molecular mechanism underlying fertility conversion in TGMS lines.

Molecular identification of the magnesium transport gene family in Brassica napus.

Magnesium (Mg2+) is an essential element for plant growth. Its transport and homeostasis in plants is mainly maintained by the MRS2/MGT of Mg2+ transporters. Little is known about the MRS2/MGT gene family in Brassica napus L. (B. napus), one of the most important oil grains. In our present study, we identified 36 putative MRS2/MGT genes (BnMGTs) from B. napus and investigated their phylogeny, expression pattern and function. These BnMGT genes were sorted into five distinguished groups by the phylogenetic analysis, and they were clearly homologous with the MRS2/MGT genes in Arabidopsis and rice. Complementation assays using the Salmonella typhimurium mutant MM281 demonstrated that the BnMGT genes were capable of mediating Mg2+ uptake and transport, with varied affinities to Mg2+. The expression pattern analysis showed that the expression of BnMGTs were tissue-specific and varied in different tissues. This work provides the molecular basis to discover the function of BnMGT gene family in plant growth and development.

A Node-Expressed Transporter OsCCX2 Is Involved in Grain Cadmium Accumulation of Rice.

Excessive cadmium (Cd) accumulation in grains of rice (Oryza sativa L.) is a risk to food security. The transporters in the nodes of rice are involved in the distribution of mineral elements including toxic elements to different tissues such as grains. However, the mechanism of Cd accumulation in grains is largely unknown. Here, we report a node-expressed transporter gene, OsCCX2, a putative cation/calcium (Ca) exchanger, mediating Cd accumulation in the grains of rice. Knockout of OsCCX2 caused a remarkable reduction of Cd content in the grains. Further study showed that disruption of this gene led to a reduced root-to-shoot translocation ratio of Cd. Moreover, Cd distribution was also disturbed in different levels of internode and leaf. OsCCX2 is localized to plasma membrane, and OsCCX2 is mainly expressed in xylem region of vascular tissues at the nodes. OsCCX2 might function as an efflux transporter, responsible for Cd loading into xylem vessels. Therefore, our finding revealed a novel Cd transporter involved in grain Cd accumulation, possibly via a Ca transport pathway in the nodes of rice.

9-cis-Epoxycarotenoid Dioxygenase 3 Regulates Plant Growth and Enhances Multi-Abiotic Stress Tolerance in Rice.

Although abscisic acid (ABA) is an important hormone that regulates seed dormancy, stomatal closure, plant development, as well as responses to environmental stimuli, the physiological mechanisms of ABA response to multiple stress in rice remain poorly understood. In the ABA biosynthetic pathway, 9-cis-epoxycarotenoid dioxygenase (NCED) is the key rate-limiting enzyme. Here, we report important functions of OsNCED3 in multi-abiotic stress tolerance in rice. The OsNCED3 is constitutively expressed in various tissues under normal condition, Its expression is highly induced by NaCl, PEG, and H2O2 stress, suggesting the roles for OsNCED3 in response to the multi-abiotic stress tolerance in rice. Compared with wild-type plants, nced3 mutants had earlier seed germination, longer post-germination seedling growth, increased sensitivity to water stress and H2O2 stress and increased stomata aperture under water stress and delayed leaf senescence. Further analysis found that nced3 mutants contained lower ABA content compared with wild-type plants, overexpression of OsNCED3 in transgenic plants could enhance water stress tolerance, promote leaf senescence and increase ABA content. We conclude that OsNCED3 mediates seed dormancy, plant growth, abiotic stress tolerance, and leaf senescence by regulating ABA biosynthesis in rice; and may provide a new strategy for improving the quality of crop.

Ectopic expression of fungal EcGDH improves nitrogen assimilation and grain yield in rice.

NADP(H)-dependent glutamate dehydrogenases (GDH) in lower organisms have stronger ammonium affinity than those in higher plants. Here we report that transgenic rice overexpressing the EcGDH from Eurotium cheralieri exhibited significantly enhanced aminating activities. Hydroponic and field tests showed that nitrogen assimilation efficiency and grain yields were markedly increased in these transgenic plants, especially at the low nitrogen conditions. These results suggest that EcGDH may have potential to be used to improve nitrogen assimilation and grain yield in rice.

RPS9M, a Mitochondrial Ribosomal Protein, Is Essential for Central Cell Maturation and Endosperm Development in Arabidopsis.

During double fertilization of angiosperms, the central cell of the female gametophyte fuses with a sperm cell to produce the endosperm, a storage tissue that nourishes the developing embryo within the seed. Although many genetic mutants defective in female gametophytic functions have been characterized, the molecular mechanisms controlling the specification and differentiation of the central cell are still not fully understood. Here, we report a mitochondrial ribosomal protein, RPS9M, is required for central cell maturation. RPS9M was highly expressed in the male and female gametophytes before and after double fertilization. The female gametophytes were defective in the rps9m mutant specifically concerning maturation of central cells. The morphological defects include unfused polar nuclei and smaller central vacuole in central cells. In addition, embryo initiation and early endosperm development were also severely affected in rps9m female gametophytes even after fertilized with wild type pollens. The RPS9M can interact with ANK6, an ankyrin-repeat protein in mitochondria previously reported to be required for fertilization. The expression pattern and mutant phenotype of RPS9M are similar to those of ANK6 as well, suggesting that RPS9M may work together with ANK6 in controlling female gametophyte development, possibly by regulating the expression of some mitochondrial proteins.

FERONIA interacts with ABI2-type phosphatases to facilitate signaling cross-talk between abscisic acid and RALF peptide in Arabidopsis.

Receptor-like kinase FERONIA (FER) plays a crucial role in plant response to small molecule hormones [e.g., auxin and abscisic acid (ABA)] and peptide signals [e.g., rapid alkalinization factor (RALF)]. It remains unknown how FER integrates these different signaling events in the control of cell growth and stress responses. Under stress conditions, increased levels of ABA will inhibit cell elongation in the roots. In our previous work, we have shown that FER, through activation of the guanine nucleotide exchange factor 1 (GEF1)/4/10-Rho of Plant 11 (ROP11) pathway, enhances the activity of the phosphatase ABA Insensitive 2 (ABI2), a negative regulator of ABA signaling, thereby inhibiting ABA response. In this study, we found that both RALF and ABA activated FER by increasing the phosphorylation level of FER. The FER loss-of-function mutant displayed strong hypersensitivity to both ABA and abiotic stresses such as salt and cold conditions, indicating that FER plays a key role in ABA and stress responses. We further showed that ABI2 directly interacted with and dephosphorylated FER, leading to inhibition of FER activity. Several other ABI2-like phosphatases also function in this pathway, and ABA-dependent FER activation required PYRABACTIN RESISTANCE (PYR)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS (RCAR)-A-type protein phosphatase type 2C (PP2CA) modules. Furthermore, suppression of RALF1 gene expression, similar to disruption of the FER gene, rendered plants hypersensitive to ABA. These results formulated a mechanism for ABA activation of FER and for cross-talk between ABA and peptide hormone RALF in the control of plant growth and responses to stress signals.