Patatin-related phospholipase pPLAIIIδ influences auxin-responsive cell morphology and organ size in Arabidopsis and Brassica napus

A group III patatin-like phospholipase gene pPLAIIIδ regulates lignin biosynthesis and influences the rate of seed germination in Arabidopsis thaliana

The lignification of plant secondary walls is an important process that provides plants with mechanical support. However, the presence of lignin in the secondary walls affects the readily availability of cellulose required in various industries, including the biofuel, paper, and textile industries. Thus, plants with less lignin are ideal for usage in such industries. Molecular studies have identified genes that regulate plant lignification, including group III plant-specific patatin-related phospholipase genes. Recent studies have reported decreased lignin content when pPLAIIIα, pPLAIIIγ (from Arabidopsis thaliana), and pPLAIIIβ (from Panax ginseng) were overexpressed in Arabidopsis. However, the role played by a closely related gene pPLAIIIδ in lignin biosynthesis has not yet been reported. In this study, we found that overexpression of the pPLAIIIδ significantly reduced the lignin content in secondary cell walls, whereas the silencing of the gene increased secondary walls lignification. Transcript level analysis showed that the key structural and regulatory genes involved in the lignin biosynthesis pathway decreased in overexpression, and increased in plants with silenced pPLAIIIδ. Further analysis revealed that pPLAIIIδ played an influential role in several physiological processes including seed germination, and chlorophyll accumulation. Moreover, the gene also influenced the size of plants and plant organs, including leaves, seeds, and root hairs. Generally, our study provides important insights toward the use of genetic engineering for lignin reduction in plants and provides information about the agronomical and physiological suitability of pPLAIIIδ transgenic plants for utilization in biomass processing industries.

Loss-of-function of gynoecium-expressed phospholipase pPLAIIγ triggers maternal haploid induction in Arabidopsis

Production of in planta haploid embryos that inherit chromosomes from only one parent can greatly increase breeding efficiency via quickly generating homozygous plants, called doubled haploid. One of the main players of in planta haploid induction is a pollen-specific phospholipase A, which is able, when mutated, to induce in vivo haploid induction in numerous monocots. However, no functional orthologous gene has been identified in dicots plants. Here, we show that loss-of-function of gynoecium-expressed phospholipase AII (pPLAIIγ) triggers maternal haploid plants in Arabidopsis, at an average rate of 1.07%. Reciprocal crosses demonstrate that haploid plants are triggered from the female side and not from the pollen, and the haploid plants carry the maternal genome. Promoter activity of pPLAIIγ shows enriched expression in the funiculus of flower development stages 13 and 18, and pPLAIIγ fused to yellow fluorescent protein reveals a plasma-membrane localization Interestingly, the polar localized PIN1 at the basal plasma membrane of the funiculus was all internalized in pplaIIγ mutants, suggesting that altered PIN1 localization in female organ could play a role in maternal haploid induction.

Integrated multi-locus genome-wide association studies and transcriptome analysis for seed yield and yield-related traits in Brassica napus

Rapeseed (Brassica napus L.), the third largest oil crop, is an important source of vegetable oil and biofuel for the world. Although the breeding and yield has been improved, rapeseed still has the lowest yield compared with other major crops. Thus, increasing rapeseed yield is essential for the high demand of vegetable oil and high-quality protein for live stocks. Silique number per plant (SN), seed per pod (SP), and 1000-seed weight (SW) are the three important factors for seed yield in rapeseed. Some yield-related traits, including plant height (PH), flowering time (FT), primary branch number (BN) and silique number per inflorescence (SI) also affect the yield per plant (YP). Using six multi-locus genome-wide association study (ML-GWAS) approaches, a total of 908 yield-related quantitative trait nucleotides (QTNs) were identified in a panel consisting of 403 rapeseed core accessions based on whole-genome sequencing. Integration of ML-GWAS with transcriptome analysis, 79 candidate genes, including BnaA09g39790D (RNA helicase), BnaA09g39950D (Lipase) and BnaC09g25980D (SWEET7), were further identified and twelve genes were validated by qRT-PCRs to affect the SW or SP in rapeseed. The distribution of superior alleles from nineteen stable QTNs in 20 elite rapeseed accessions suggested that the high-yielding accessions contained more superior alleles. These results would contribute to a further understanding of the genetic basis of yield-related traits and could be used for crop improvement in B. napus.

Patatin-like phospholipase A-induced alterations in lipid metabolism and jasmonic acid production affect the heat tolerance of Gracilariopsis lemaneiformis

High temperatures seriously limit the growth and productivity of Gracilariopsis lemaneiformis. By hydrolyzing glycerolipids into lysophospholipids (LPs) and free fatty acids (FFAs), patatin-like phospholipase A (pPLA) plays an important role in stress responses. GlpPLA expression was up-regulated under heat stress, however, the regulation of pPLA in heat tolerance of G. lemaneiformis is unknown. In this study, G. lemaneiformis under heat stress was treated with bromoenololide (BEL), a chemical inhibitor of pPLA, to evaluate the cellular function of pPLA in this species. When pPLA was inhibited through BEL treatment, the sensitivity of G. lemaneiformis to heat stress increased and the biomass and maximum and effective quantum yield of photosystem II decreased. Moreover, BEL treatment resulted in a significant decrease in many lipid molecular species, all of which are mainly composed of 16C, 18C, and 20C fatty acids. Consistently, FFA levels and LPs contents in G. lemaneiformis under BEL treatment showed a significant decrease. The first step in the synthesis of jasmonic acid (JA) is the lipoxygenase (LOX)-mediated oxygenation of linolenic acid (C18:3). BEL treatment decreased JA and C18:3 accumulation and markedly downregulated the expression of GILOX under heat stress. Together, these results indicate that pPLA is closely related to the growth of G. lemaneiformis under heat stress, and pPLA is involved in the lipid metabolism and JA biosynthesis of G. lemaneiformis in response to heat stress. This research broadens the understanding of the heat stress adaptation mechanism of G. lemaneiformis.

The functions of phospholipases and their hydrolysis products in plant growth, development and stress responses

Cell membranes are the initial site of stimulus perception from environment and phospholipids are the basic and important components of cell membranes. Phospholipases hydrolyze membrane lipids to generate various cellular mediators. These phospholipase-derived products, such as diacylglycerol, phosphatidic acid, inositol phosphates, lysophopsholipids, and free fatty acids, act as second messengers, playing vital roles in signal transduction during plant growth, development, and stress responses. This review focuses on the structure, substrate specificities, reaction requirements, and acting mechanism of several phospholipase families. It will discuss their functional significance in plant growth, development, and stress responses. In addition, it will highlight some critical knowledge gaps in the action mechanism, metabolic and signaling roles of these phospholipases and their products in the context of plant growth, development and stress responses.

Overexpression of pPLAIIIγ in Arabidopsis Reduced Xylem Lignification of Stem by Regulating Peroxidases

Patatin-related phospholipases A (pPLAs) are a group of plant-specific acyl lipid hydrolases that share less homology with phospholipases than that observed in other organisms. Out of the three known subfamilies (pPLAI, pPLAII, and pPLAIII), the pPLAIII member of genes is particularly known for modifying the cell wall structure, resulting in less lignin content. Overexpression of pPLAIIIα and ginseng-derived PgpPLAIIIβ in Arabidopsis and hybrid poplar was reported to reduce the lignin content. Lignin is a complex racemic phenolic heteropolymer that forms the key structural material supporting most of the tissues in plants and plays an important role in the adaptive strategies of vascular plants. However, lignin exerts a negative impact on the utilization of plant biomass in the paper and pulp industry, forage digestibility, textile industry, and production of biofuel. Therefore, the overexpression of pPLAIIIγ in Arabidopsis was analyzed in this study. This overexpression led to the formation of dwarf plants with altered anisotropic growth and reduced lignification of the stem. Transcript levels of lignin biosynthesis-related genes, as well as lignin-specific transcription factors, decreased. Peroxidase-mediated oxidation of monolignols occurs in the final stage of lignin polymerization. Two secondary cell wall-specific peroxidases were downregulated following lowered H₂O₂ levels, which suggests a functional role of peroxidase in the reduction of lignification by pPLAIIIγ when overexpressed in Arabidopsis.

The Reduced Longitudinal Growth Induced by Overexpression of pPLAIIIγ Is Regulated by Genes Encoding Microtubule-Associated Proteins

There are three subfamilies of patatin-related phospholipase A (pPLA) group of genes: pPLAI, pPLAII, and pPLAIII. Among the four members of pPLAIIIs (α, β, γ, δ), the overexpression of three isoforms (α, β, and δ) displayed distinct morphological growth patterns, in which the anisotropic cell expansion was disrupted. Here, the least studied pPLAIIIγ was characterized, and it was found that the overexpression of pPLAIIIγ in Arabidopsis resulted in longitudinally reduced cell expansion patterns, which are consistent with the general phenotype induced by pPLAIIIs overexpression. The microtubule-associated protein MAP18 was found to be enriched in a pPLAIIIδ overexpressing line in a previous study. This indicates that factors, such as microtubules and ethylene biosynthesis, are involved in determining the radial cell expansion patterns. Microtubules have long been recognized to possess functional key roles in the processes of plant cells, including cell division, growth, and development, whereas ethylene treatment was reported to induce the reorientation of microtubules. Thus, the possible links between the altered anisotropic cell expansion and microtubules were studied. Our analysis revealed changes in the transcriptional levels of microtubule-associated genes, as well as phospholipase D (PLD) genes, upon the overexpression of pPLAIIIγ. Overall, our results suggest that the longitudinally reduced cell expansion observed in pPLAIIIγ overexpression is driven by microtubules via transcriptional modulation of the PLD and MAP genes. The altered transcripts of the genes involved in ethylene-biosynthesis in pPLAIIIγOE further support the conclusion that the typical phenotype is derived from the link with microtubules.

GhPLP2 Positively Regulates Cotton Resistance to Verticillium Wilt by Modulating Fatty Acid Accumulation and Jasmonic Acid Signaling Pathway

Patatin-like proteins (PLPs) have non-specific lipid acyl hydrolysis (LAH) activity, which can hydrolyze membrane lipids into fatty acids and lysophospholipids. The vital role of PLPs in plant growth and abiotic stress has been well documented. However, the function of PLPs in plant defense responses against pathogens is still poorly understood. Here, we isolated and identified a novel cotton (Gossypium hirsutum) PLP gene GhPLP2. The expression of GhPLP2 was induced upon treatment with Verticillium dahliae, the signaling molecules jasmonic acid (JA) and ethylene (ETH) in cotton plants. Subcellular localization revealed that GhPLP2 was localized to the plasma membrane. GhPLP2-silenced cotton plants were more susceptible to infection by V. dahliae, while the overexpression of GhPLP2 in Arabidopsis enhanced its resistance to V. dahliae, which was apparent as mild symptoms, and a decrease in the disease index and fungal biomass. The hypersensitive response, deposition of callose, and H₂O₂ accumulation triggered by V. dahliae elicitor were reduced in GhPLP2-silenced cotton plants. The overexpression of GhPLP2 in Arabidopsis resulted in the accumulation of linoleic acid (LA, 18:2) and α-linolenic acid (ALA, 18:3) and facilitated the biosynthesis of JA and JA-mediated defensive responses. GhPLP2 silencing in cotton plants consistently reduced the accumulation of linoleic acid (LA, 18:2) and α-linolenic acid (ALA, 18:3) and suppressed the biosynthesis of JA and the defensive responses mediated by JA. These results indicate that GhPLP2 is involved in the resistance of cotton to V. dahliae by maintaining fatty acid metabolism pools for JA biosynthesis and activating the JA signaling pathway.

GhPLP2 Positively Regulates Cotton Resistance to Verticillium Wilt by Modulating Fatty Acid Accumulation and Jasmonic Acid Signaling Pathway

Patatin-like proteins (PLPs) have non-specific lipid acyl hydrolysis (LAH) activity, which can hydrolyze membrane lipids into fatty acids and lysophospholipids. The vital role of PLPs in plant growth and abiotic stress has been well documented. However, the function of PLPs in plant defense responses against pathogens is still poorly understood. Here, we isolated and identified a novel cotton (Gossypium hirsutum) PLP gene GhPLP2. The expression of GhPLP2 was induced upon treatment with Verticillium dahliae, the signaling molecules jasmonic acid (JA) and ethylene (ETH) in cotton plants. Subcellular localization revealed that GhPLP2 was localized to the plasma membrane. GhPLP2-silenced cotton plants were more susceptible to infection by V. dahliae, while the overexpression of GhPLP2 in Arabidopsis enhanced its resistance to V. dahliae, which was apparent as mild symptoms, and a decrease in the disease index and fungal biomass. The hypersensitive response, deposition of callose, and H₂O₂ accumulation triggered by V. dahliae elicitor were reduced in GhPLP2-silenced cotton plants. The overexpression of GhPLP2 in Arabidopsis resulted in the accumulation of linoleic acid (LA, 18:2) and α-linolenic acid (ALA, 18:3) and facilitated the biosynthesis of JA and JA-mediated defensive responses. GhPLP2 silencing in cotton plants consistently reduced the accumulation of linoleic acid (LA, 18:2) and α-linolenic acid (ALA, 18:3) and suppressed the biosynthesis of JA and the defensive responses mediated by JA. These results indicate that GhPLP2 is involved in the resistance of cotton to V. dahliae by maintaining fatty acid metabolism pools for JA biosynthesis and activating the JA signaling pathway.

Genome-wide association study reveals a patatin-like lipase relating to the reduction of seed oil content in Brassica napus

BACKGROUND

Rapeseed (Brassica napus L.) is an important oil crop world-widely cultivated, and seed oil content (SOC) is one of the most important traits for rapeseed. To increase SOC, many efforts for promoting the function of genes on lipid biosynthesis pathway have been previously made. However, seed oil formation is a dynamic balance between lipid synthesis and breakdown. It is, therefore, also reasonable to weaken or eliminate the function of genes involved in lipid degradation for a higher final SOC.

RESULTS

We applied a genome-wide association study (GWAS) on SOC in a collection of 290 core germplasm accessions. A total of 2,705,480 high-quality SNPs were used in the GWAS, and we identified BnaC07g30920D, a patatin-like lipase (PTL) gene, that was associated with SOC. In particular, six single-nucleotide-polymorphisms (SNPs) in the promoter region of BnaC07g30920D were associated with the significant reduction of SOC, leading to a 4.7-6.2% reduction of SOCs. We performed in silico analysis to show a total of 40 PTLs, which were divided into four clades, evenly distributed on the A and C subgenomes of Brassica napus. RNA-seq analysis unveiled that BnPTLs were preferentially expressed in reproductive tissues especially maturing seeds.

CONCLUSIONS

We identified BnaC07g30920D, a BnPTL gene, that was associated with SOC using GWAS and performed in silico analysis of 40 PTLs in Brassica napus. The results enrich our knowledge about the SOC formation in rapeseed and facilitate the future study in functional characterization of BnPTL genes.

BnA10.RCO, a homeobox gene, positively regulates leaf lobe formation in Brassica napus L

BnA10.RCO positively regulates the development of leaf lobes in Brassica napus, and cis-regulatory divergences cause the different allele effects. The functional importance of lobed leaves in rapeseed (Brassica napus L.) has been identified with potential advantages for high-density planting and hybrid production. Our previous studies indicated that the tandemly duplicated LMI1-like genes BnA10. RCO and BnA10.LMI1 are candidate genes of an incompletely dominant locus, which is responsible for the lobed-leaf shape in rapeseed. We provided strong evidence that BnA10.LMI1 positively regulates leaf lobe formation. Here, we show that BnA10.RCO is a nucleus-specific protein, encoding an HD-ZIP I transcription factor, which is responsible for the lobed-leaf shape in rapeseed. Sequence analysis of parental alleles revealed that no vital sequence variation was detected in the coding sequence of BnA10.RCO, whereas abundant variations were identified in the regulatory regions. Consistent with this finding, the expression level of BnRCO was substantially elevated in the lobed-leaved parent HY compared with its near-isogenic line. Moreover, the altered expression of BnA10.RCO in transgenic lines showed a positive connection with leaf complexity without a substantial change in BnLMI1 transcript level. Furthermore, CRISPR/Cas9-induced null mutations of BnA10.RCO in the lobed-leaved parent HY were sufficient to produce an unlobed leaf without alteration in BnLMI1 transcript level. Our results indicate that BnA10.RCO functions together with BnA10.LMI1 to positively determine the lobed-leaf development, providing a fundamental basis for crop improvement by targeting leaf shape in rapeseed.

Phospholipase pPLAIIIα Increases Germination Rate and Resistance to Turnip Crinkle Virus when Overexpressed

Patatin-related phospholipase As (pPLAs) are major hydrolases acting on acyl-lipids and play important roles in various plant developmental processes. pPLAIII group members, which lack a canonical catalytic Ser motif, have been less studied than other pPLAs. We report here the characterization of pPLAIIIα in Arabidopsis (Arabidopsis thaliana) based on the biochemical and physiological characterization of pPLAIIIα knockouts, complementants, and overexpressors, as well as heterologous expression of the protein. In vitro activity assays on the purified recombinant protein showed that despite lack of canonical phospholipase motifs, pPLAIIIα had a phospholipase A activity on a wide variety of phospholipids. Overexpression of pPLAIIIα in Arabidopsis resulted in a decrease in many lipid molecular species, but the composition in major lipid classes was not affected. Fluorescence tagging indicated that pPLAIIIα localizes to the plasma membrane. Although Arabidopsis pplaIIIα knockout mutants showed some phenotypes comparable to other pPLAIIIs, such as reduced trichome length and increased hypocotyl length, control of seed size and germination were identified as distinctive pPLAIIIα-mediated functions. Expression of some PLD genes was strongly reduced in the pplaIIIα mutants. Overexpression of pPLAIIIα caused increased resistance to turnip crinkle virus, which associated with a 2-fold higher salicylic acid/jasmonic acid ratio and an increased expression of the defense gene pathogenesis-related protein1. These results therefore show that pPLAIIIα has functions that overlap with those of other pPLAIIIs but also distinctive functions, such as the control of seed germination. This study also provides new insights into the pathways downstream of pPLAIIIα.

Patatin-Related Phospholipase pPLAIIIγ Involved in Osmotic and Salt Tolerance in Arabidopsis

Patatin-related phospholipases (pPLAs) are acyl-hydrolyzing enzymes implicated in various processes, including lipid metabolism, signal transduction, plant growth and stress responses, but the function for many specific pPLAs in plants remains unknown. Here we determine the effect of patatin-related phospholipase A pPLAIIIγ on Arabidopsis response to abiotic stress. Knockout of pPLAIIIγ rendered plants more sensitive whereas overexpression of pPLAIIIγ enhanced plant tolerance to NaCl and drought in seed germination and seedling growth. The pPLAIIIγ-knockout and overexpressing seedlings displayed a lower and higher level of lysolipids and free fatty acids than that of wild-type plants in response to NaCl stress, respectively. These results indicate that pPLAIIIγ acts a positive regulator of salt and osmatic stress tolerance in Arabidopsis.

Castor patatin-like phospholipase A IIIβ facilitates removal of hydroxy fatty acids from phosphatidylcholine in transgenic Arabidopsis seeds

Castor patatin-like phospholipase A IIIβ facilitates the exclusion of hydroxy fatty acids from phosphatidylcholine in developing transgenic Arabidopsis seeds. Hydroxy fatty acids (HFAs) are industrial useful, but their major natural source castor contains toxic components. Although expressing a castor OLEATE 12-HYDROXYLASE in Arabidopsis thaliana leads to the synthesis of HFAs in seeds, a high proportion of the HFAs are retained in phosphatidylcholine (PC). Thus, the liberation of HFA from PC seems to be critical for obtaining HFA-enriched seed oils. Plant phospholipase A (PLA) catalyzes the hydrolysis of PC to release fatty acyl chains that can be subsequently channeled into triacylglycerol (TAG) synthesis or other metabolic pathways. To further our knowledge regarding the function of PLAs from HFA-producing plant species, two class III patatin-like PLA cDNAs (pPLAIIIβ or pPLAIIIδ) from castor or Physaria fendleri were overexpressed in a transgenic line of A. thaliana producing C18-HFA, respectively. Only the overexpression of RcpPLAIIIβ resulted in a significant reduction in seed HFA content with concomitant changes in fatty acid composition. Reductions in HFA content occurred in both PC and TAG indicating that HFAs released from PC were not incorporated into TAG. These results suggest that RcpPLAIIIβ may catalyze the removal of HFAs from PC in the developing seeds synthesizing these unusual fatty acids.

Ginseng-derived patatin-related phospholipase PgpPLAIIIβ alters plant growth and lignification of xylem in hybrid poplars

Patatin-liked phospholipase A (pPLAs) are major lipid acyl hydrolases that participate in various biological functions in plant growth and development. Previously, a ginseng-derived pPLAIII homolog was reported to reduce lignin content in Arabidopsis. This led us to evaluate its possible usefulness as a biomass source in wood plant. Herein, we report that there are six members in the pPLAIII gene family in poplar. Overexpression of pPLAIIIβ derived from ginseng resulted in a reduced plant height with radially expanded stem growth in hybrid poplars. Compared with the wild type (WT), the chlorophyll content was increased in the overexpression poplar lines, whereas the leaf size was smaller. The secondary cell wall structure in overexpression lines was also altered, exhibiting reduced lignification in the xylem. Two transcription factors, MYB92 and MYB152, which control lignin biosynthesis, were downregulated in the overexpression lines. The middle xylem of the overexpression line showed heavy thickening, making it thicker than the other xylem parts and the WT xylem, which rather could have been contributed by the presence of more cellulose in the selected surface area. Taken together, the results suggest that PgpPLAIIIβ plays a role not only in cell elongation patterns, but also in determining the secondary cell wall composition.

CRISPR/Cas9-mediated genome editing reveals differences in the contribution of INDEHISCENT homologues to pod shatter resistance in Brassica napus L

The INDEHISCENT (IND) and ALCATRAZ (ALC) gene homologues have been reported to be essential for dehiscence of fruits in Brassica species. But their functions for pod shatter resistance in Brassica napus, an important oil crops, are not well understood. Here, we assessed the functions of these two genes in rapeseed using CRISPR/Cas9 technology. The induced mutations were stably transmitted to successive generations, and a variety of homozygous mutants with loss-of-function alleles of the target genes were obtained for phenotyping. The results showed that the function of BnIND gene is essential for pod shatter and highly conserved in Brassica species, whereas the BnALC gene appears to have limited potential for rapeseed shatter resistance. The homoeologous copies of the BnIND gene have partially redundant roles in rapeseed pod shatter, with BnA03.IND exhibiting higher contributions than BnC03.IND. Analysis of data obtained from the gene expression and sequence variations of gene copies revealed that cis-regulatory divergences alter gene expression and underlie the functional differentiation of BnIND homologues. Collectively, our results generate valuable resources for rapeseed breeding programs, and more importantly provide a strategy to improve polyploid crops.

Functional diversity of glycerolipid acylhydrolases in plant metabolism and physiology

Most current knowledge about plant lipid metabolism has focused on the biosynthesis of lipids and their transport between different organelles. However, lipid composition changes during development and in response to environmental cues often go beyond adjustments of lipid biosynthesis. When lipids have to be removed to adjust the extent of membranes during down regulation of photosynthesis, or lipid composition has to be adjusted to alter the biophysical properties of membranes, or lipid derived chemical signals have to be produced, lipid-degrading enzymes come into play. This review focuses on glycerolipid acylhydrolases that remove acyl groups from glycerolipids and will highlight their roles in lipid remodeling and lipid-derived signal generation. One emerging theme is that these enzymes are involved in the dynamic movement of acyl groups through different lipid pools, for example from polar membrane lipids to neutral lipids sequestered in lipid droplets during de novo triacylglycerol synthesis. Another example of acyl group sequestration in the form of triacylglycerols in lipid droplets is membrane lipid remodeling in response to abiotic stresses. Fatty acids released for membrane lipids can also give rise to potent signaling molecules and acylhydrolases are therefore often the first step in initiating the formation of these lipid signals.

Recent Advances in the Cellular and Developmental Biology of Phospholipases in Plants

Phospholipases (PLs) are lipid-hydrolyzing enzymes known to have diverse signaling roles during plant abiotic and biotic stress responses. They catalyze lipid remodeling, which is required to generate rapid responses of plants to environmental cues. Moreover, they produce second messenger molecules, such as phosphatidic acid (PA) and thus trigger or modulate signaling cascades that lead to changes in gene expression. The roles of phospholipases in plant abiotic and biotic stress responses have been intensively studied. Nevertheless, emerging evidence suggests that they also make significant contributions to plants' cellular and developmental processes. In this mini review, we summarized recent advances in the study of the cellular and developmental roles of phospholipases in plants.

The Role of Gβ Protein in Controlling Cell Expansion via Potential Interaction with Lipid Metabolic Pathways

Heterotrimeric G-proteins influence almost all aspects of plant growth, development, and responses to biotic and abiotic stresses in plants, likely via their interaction with specific effectors. However, the identity of such effectors and their mechanism of action are mostly unknown. While investigating the roles of different G-protein subunits in modulating the oil content in Camelina (Camelina sativa), an oil seed crop, we uncovered a role of Gβ proteins in controlling anisotropic cell expansion. Knockdown of Gβ genes causes reduced longitudinal and enhanced transverse expansion, resulting in altered cell, tissue, and organ shapes in transgenic plants during vegetative and reproductive development. These plants also exhibited substantial changes in their fatty acid and phospholipid profiles, which possibly leads to the increased oil content of the transgenic seeds. This increase is potentially caused by the direct interaction of Gβ proteins with a specific patatin-like phospholipase, pPLAIIIδ. Camelina plants with suppressed Gβ expression exhibit higher lipase activity, and show phenotypes similar to plants overexpressing pPLAIIIδ, suggesting that the Gβ proteins are negative regulators of pPLAIIIδ. These results reveal interactions between the G-protein-mediated and lipid signaling/metabolic pathways, where specific phospholipases may act as effectors that control key developmental and environmental responses of plants.