Plant Journal
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A quantitative trait locus <i>GW6</i> controls rice grain size and yield through the gibberellin pathway SUMMARY Grain size is one of the essential components determining rice yield and is a target for both domestication and artificial breeding. Gibberellins (GAs) are diterpenoid phytohormones that influence diverse aspects of plant growth and development. Several quantitative trait loci (QTLs) have been identified that control grain size through phytohormone regulation. However, little is known about the role of GAs in the control of grain size. Here we report the cloning and characterization of a QTL, GW6 (GRAIN WIDTH 6 ), which encodes a GA‐regulated GAST family protein and positively regulates grain width and weight. GW6 is highly expressed in the young panicle and increases grain width by promoting cell expansion in the spikelet hull. Knockout of GW6 exhibits reduced grain size and weight, whereas overexpression of GW6 results in increased grain size and weight. GW6 is induced by GA and its knockout downregulates the expression of GA biosynthesis genes and decreases GA content in the young panicle. We found that a natural variation in the cis element CAAT‐box in the promoter of GW6 is associated with its expression level and grain width and weight. Furthermore, introduction of GW6 to Oryza indica variety HJX74 can lead to a 10.44% increase in rice grain yield, indicating that GW6 has great potential to improve grain yield in rice.
Plant Journal - Tập 103 Số 3 - Trang 1174-1188 - 2020
Mutants of <i>Arabidopsis thaliana</i> with altered cell wall polysaccharide composition To analyze the synthesis, structure and function of the plant cell wall by a genetic approach, 5200 chemically mutagenized Arabidopsis plants were screened for changes in the monosaccharide composition of hydrolyzed cell wall material by gas chromatography of alditol acetates. This screening procedure identified 23 mutant lines representing 11 different loci designated mur1 to mur11 . The mur lines fall into essentially three groups: (1) complete absence of a monosaccharide, (2) significant reduction in the amount of a single monosaccharide, and (3) complex alterations in the relative amounts of several monosaccharides. All mutants in the first category represent alleles of the mur1 locus, and are deficient in the de novo synthesis of fucose. Mutants with reductions in a single monosaccharide have been identified for fucose (mur2, mur3 ), arabinose (mur4, mur5, mur6, mur7 ), and rhamnose (mur8 ). Mutants with complex changes in monosaccharide composition are represented by the mur9 , mur10 and mur11 loci. Most of the mutant lines did not show obvious morphological or physiological alterations; however, lines mur1, mur9 and mur10 co‐segregated with reduced vigor or dwarfism of the plants. These results demonstrate the feasibility of identifying plants with altered cell wall compositions via a biochemical screening procedure. The availability of these mutants provides novel opportunities to study the functions of cell wall polysaccharides, gain insight into the biosynthesis of cell wall material, and clone cell wall‐related genes.
Plant Journal - Tập 12 Số 2 - Trang 335-345 - 1997
Molecular characterisation of a membrane‐bound galactosyltransferase of plant cell wall matrix polysaccharide biosynthesis Summary Galactomannan biosynthesis in vitro is catalysed by membrane preparations from developing fenugreek seed endosperms. Two enzymes interact: a GDP‐mannose dependent (1→4)‐β‐d ‐mannan synthase and a UDP‐galactose dependent (1→6)‐α‐d ‐galactosyltransferase. The statistical distribution of galactosyl substituents along the mannan backbone, and the degree of galactose substitution of the primary product of galactomannan biosynthesis appear to be regulated by the specificity of the galactosyltransferase. We now report the detergent solubilisation of the fenugreek galactosyltransferase with retention of activity, the identification on gels of a putative 51 kDa galactosyltransferase protein, and the isolation, cloning and sequencing of the corresponding cDNA. The solubilised galactosyltransferase has an absolute requirement for added acceptor substrates. Beta‐(1→4)‐linked d ‐manno‐oligosaccharides with chain lengths greater than or equal to 5 acted as acceptors, as did galactomannans of low to medium galactose‐substitution. The putative galactosyltransferase cDNA encodes a 51282 Da protein, with a single transmembrane alpha helix near the N terminus. We have also confirmed the identity of the galactosyltransferase by inserting the cDNA in frame into the genome of the methylotrophic yeast Pichia pastoris under the control of an AOX promoter and the yeast alpha secretion factor and observing the secretion of galactomannan α‐galactosyltransferase activity. Particularly high activities were observed when a truncated sequence, lacking the membrane‐spanning helix, was expressed.
Plant Journal - Tập 19 Số 6 - Trang 691-697 - 1999
Osa‐miR164a targets <i>Os<scp>NAC</scp>60</i> and negatively regulates rice immunity against the blast fungus <i>Magnaporthe oryzae</i> Summary Exploring the regulatory mechanism played by endogenous rice miRNA s in defense responses against the blast disease is of great significance in both resistant variety breeding and disease control management. We identified rice defense‐related miRNA s by comparing rice miRNA expression patterns before and after Magnaporthe oryzae strain Guy11 infection. We discovered that osa‐miR164a expression reduced upon Guy11 infection at both early and late stages, which was perfectly associated with the induced expression of its target gene, OsNAC 60 . OsNAC 60 encodes a transcription factor, over‐expression of which enhanced defense responses, such as increased programmed cell death, greater ion leakage, more reactive oxygen species accumulation and callose deposition, and upregulation of defense‐related genes. By using transgenic rice over‐expressing osa‐miR164a, and a transposon insertion mutant of OsNAC 60 , we showed that when the miR164a/OsNAC 60 regulatory module was dysfunctional, rice developed significant susceptibility to Guy11 infection. The co‐expression of OsNAC 60 and osa‐miR164a abolished the OsNAC 60 activity, but not its synonymous mutant. We further validated that this regulatory module is conserved in plant resistance to multiple plant diseases, such as the rice sheath blight, tomato late blight, and soybean root and stem rot diseases. Our results demonstrate that the miR164a/OsNAC 60 regulatory module manipulates rice defense responses to M. oryzae infection. This discovery is of great potential for resistant variety breeding and disease control to a broad spectrum of pathogens in the future.
Plant Journal - Tập 95 Số 4 - Trang 584-597 - 2018
Interplay of miR164, <i>CUP‐SHAPED COTYLEDON</i> genes and <i>LATERAL SUPPRESSOR</i> controls axillary meristem formation in <i>Arabidopsis thaliana</i> Summary Aerial architecture in higher plants is established post‐embryonically by the inception of new meristems in the axils of leaves. These axillary meristems develop into side shoots or flowers. In Arabidopsis, the NAC domain transcription factors CUP SHAPED COTYLEDON1 (CUC1 ), CUC2 and CUC3 function redundantly in initiating the shoot apical meristem and establishing organ boundaries. Transcripts of CUC1 and CUC2 are targeted for degradation by miR164. In this study, we show that cuc3‐2 mutants are impaired in axillary meristem initiation. Overexpression of miR164 in the cuc3‐2 mutant caused an almost complete block of axillary meristem formation. Conversely, mir164 mutants and plants harbouring miR164‐resistant alleles of CUC1 or CUC2 developed accessory buds in leaf axils. Collectively, these experiments reveal that, in addition to CUC3 , redundant functions of CUC1 and CUC2 as well as miR164 regulation are required for the establishment of axillary meristems. Studies on LAS transcript accumulation in mir164 triple mutants and cuc3‐2 plants overexpressing miR164 suggest that regulation of axillary meristem formation by miR164 is mediated through CUC1 and CUC2 , which in turn regulate LAS .
Plant Journal - Tập 55 Số 1 - Trang 65-76 - 2008
Duplicated <i>P5CS</i> genes of Arabidopsis play distinct roles in stress regulation and developmental control of proline biosynthesis Summary Δ‐1‐pyrroline‐5‐carboxylate synthetase enzymes, which catalyse the rate‐limiting step of proline biosynthesis, are encoded by two closely related P5CS genes in Arabidopsis. Transcription of the P5CS genes is differentially regulated by drought, salinity and abscisic acid, suggesting that these genes play specific roles in the control of proline biosynthesis. Here we describe the genetic characterization of p5cs insertion mutants, which indicates that P5CS1 is required for proline accumulation under osmotic stress. Knockout mutations of P5CS1 result in the reduction of stress‐induced proline synthesis, hypersensitivity to salt stress, and accumulation of reactive oxygen species. By contrast, p5cs2 mutations cause embryo abortion during late stages of seed development. The desiccation sensitivity of p5cs2 embryos does not reflect differential control of transcription, as both P5CS mRNAs are detectable throughout embryonic development. Cellular localization studies with P5CS –GFP gene fusions indicate that P5CS1 is sequestered into subcellular bodies in embryonic cells, where P5CS2 is dominantly cytoplasmic. Although proline feeding rescues the viability of mutant embryos, p5cs2 seedlings undergo aberrant development and fail to produce fertile plants even when grown on proline. In seedlings, specific expression of P5CS2–GFP is seen in leaf primordia where P5CS1–GFP levels are very low, and P5CS2–GFP also shows a distinct cell‐type‐specific and subcellular localization pattern compared to P5CS1–GFP in root tips, leaves and flower organs. These data demonstrate that the Arabidopsis P5CS enzymes perform non‐redundant functions, and that P5CS1 is insufficient for compensation of developmental defects caused by inactivation of P5CS2 .
Plant Journal - Tập 53 Số 1 - Trang 11-28 - 2008
Phospholipase C5 (NPC5) is involved in galactolipid accumulation during phosphate limitation in leaves of Arabidopsis Summary The replacement of phospholipids by galacto‐ and sulfolipids in plant membranes represents an important adaptive process for growth on phosphate‐limiting soils. Gene expression and lipid analyses revealed that the MYB transcription factor PHR1 that has been previously shown to regulate phosphate responses is not a major factor controlling membrane lipid changes. Candidate genes for phospholipid degradation were selected based on induction of expression during phosphate deprivation. Lipid measurements in the corresponding Arabidopsis mutants revealed that the non‐specific phospholipase C5 (NPC5) is required for normal accumulation of digalactosyldiacylglycerol (DGDG) during phosphate limitation in leaves. The growth and DGDG content of a double mutant npc5 pho1 (between npc5 and the phosphate‐deficient pho1 mutant) are reduced compared to parental lines. The amount of DGDG increases from approximately 15 mol% to 22 mol% in npc5 , compared to 28 mol% in wild‐type, indicating that NPC5 is responsible for approximately 50% of the DGDG synthesized during phosphate limitation in leaves. Expression in Escherichia coli revealed that NPC5 shows phospholipase C activity on phosphatidylcholine and phosphatidylethanolamine. A double mutant of npc5 and pldζ2 (carrying a mutation in the phospholipase Dζ2 gene) was generated. Lipid measurements in npc5 pldζ2 indicated that the contribution of PLDζ2 to DGDG production in leaves is negligible. In contrast to the chloroplast envelope localization of galactolipid synthesis enzymes, NPC5 localizes to the cytosol, suggesting that, during phosphate limitation, soluble NPC5 associates with membranes where it contributes to the conversion of phospholipids to diacylglycerol, the substrate for galactolipid synthesis.
Plant Journal - Tập 56 Số 1 - Trang 28-39 - 2008
Improving phosphorus use efficiency: a complex trait with emerging opportunities Summary Phosphorus (P) is one of the essential nutrients for plants, and is indispensable for plant growth and development. P deficiency severely limits crop yield, and regular fertilizer applications are required to obtain high yields and to prevent soil degradation. To access P from the soil, plants have evolved high‐ and low‐affinity Pi transporters and the ability to induce root architectural changes to forage P. Also, adjustments of numerous cellular processes are triggered by the P starvation response, a tightly regulated process in plants. With the increasing demand for food as a result of a growing population, the demand for P fertilizer is steadily increasing. Given the high costs of fertilizers and in light of the fact that phosphate rock, the source of P fertilizer, is a finite natural resource, there is a need to enhance P fertilizer use efficiency in agricultural systems and to develop plants with enhanced Pi uptake and internal P‐use efficiency (PUE ). In this review we will provide an overview of continuing relevant research and highlight different approaches towards developing crops with enhanced PUE . In this context, we will summarize our current understanding of root responses to low phosphorus conditions and will emphasize the importance of combining PUE with tolerance of other stresses, such as aluminum toxicity. Of the many genes associated with Pi deficiency, this review will focus on those that hold promise or are already at an advanced stage of testing (OsPSTOL 1 , AVP 1 , PHO 1 and OsPHT 1;6 ). Finally, an update is provided on the progress made exploring alternative technologies, such as phosphite fertilizer.
Plant Journal - Tập 90 Số 5 - Trang 868-885 - 2017
Different effects of phospholipase Dζ2 and non‐specific phospholipase C4 on lipid remodeling and root hair growth in Arabidopsis response to phosphate deficiency Summary Phosphate (Pi) deficiency in soils is a major limiting factor for plant growth. In response to Pi deprivation, one prominent metabolic adaptation in plants is the decrease in membrane phospholipids that consume approximately one‐third cellular Pi. The level of two phospholipid‐hydrolyzing enzymes, phospholipase Dζ2 (PLDζ2) and non‐specific phospholipase C4 (NPC4), is highly induced in Pi‐deprived Arabidopsis. To determine the role of PLDζ2 and NPC4 in plant growth under Pi limitation, Arabidopsis plants deficient in both PLDζ2 and NPC4 (npc4pldζ2 ) were generated and characterized. Lipid remodeling in leaves and roots was analyzed at three different durations of Pi deficiency. NPC4 affected lipid changes mainly in roots at an early stage of Pi deprivation, whereas PLDζ2 exhibited a more overt effect on lipid remodeling in leaves at a later stage of Pi deprivation. Pi deficiency‐induced galactolipid increase and phospholipid decrease were impeded in pldζ2 and npc4pldζ2 plants. In addition, seedlings of npc4pldζ2 had the same root hair density as pldζ2 but shorter root hair length than pldζ2 in response to Pi deficiency. The loss of NPC4 decreased root hair length but had no effect on root hair density. These data suggest that PLDζ2 and NPC4 mediate the Pi deprivation‐induced lipid remodeling in a tissue‐ and time‐specific manner. PLDζ2 and NPC4 have distinctively different roles in root hair growth and development in response to Pi deprivation; PLDζ2 negatively modulates root hair density and length, whereas NPC4 promotes root hair elongation.
Plant Journal - Tập 94 Số 2 - Trang 315-326 - 2018
Successful high‐level accumulation of fish oil omega‐3 long‐chain polyunsaturated fatty acids in a transgenic oilseed crop Summary Omega‐3 (also called n ‐3) long‐chain polyunsaturated fatty acids (≥C20; LC‐PUFAs) are of considerable interest, based on clear evidence of dietary health benefits and the concurrent decline of global sources (fish oils). Generating alternative transgenic plant sources of omega‐3 LC‐PUFAs, i.e. eicosapentaenoic acid (20:5 n ‐3, EPA) and docosahexaenoic acid (22:6 n ‐3, DHA) has previously proved problematic. Here we describe a set of heterologous genes capable of efficiently directing synthesis of these fatty acids in the seed oil of the crop Camelina sativa , while simultaneously avoiding accumulation of undesirable intermediate fatty acids. We describe two iterations: RRes_EPA in which seeds contain EPA levels of up to 31% (mean 24%), and RRes_DHA, in which seeds accumulate up to 12% EPA and 14% DHA (mean 11% EPA and 8% DHA). These omega‐3 LC‐PUFA levels are equivalent to those in fish oils, and represent a sustainable, terrestrial source of these fatty acids. We also describe the distribution of these non‐native fatty acids within C. sativa seed lipids, and consider these data in the context of our current understanding of acyl exchange during seed oil synthesis.
Plant Journal - Tập 77 Số 2 - Trang 198-208 - 2014
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