MtPIN1 and MtPIN3 Play Dual Roles in Regulation of Shade Avoidance Response under Different Environments in Medicago truncatula

Polar auxin transport mediated by PIN-FORMED (PIN) proteins is critical for plant growth and development. As an environmental cue, shade stimulates hypocotyls, petiole, and stem elongation by inducing auxin synthesis and asymmetric distributions, which is modulated by PIN3,4,7 in Arabidopsis. Here, we characterize the MtPIN1 and MtPIN3, which are the orthologs of PIN3,4,7, in model legume species Medicago truncatula. Under the low Red:Far-Red (R:FR) ratio light, the expression of MtPIN1 and MtPIN3 is induced, and shadeavoidance response is disrupted in mtpin1 mtpin3 double mutant, indicating that MtPIN1 and MtPIN3 have a conserved function in shade response. Surprisingly, under the normal growth condition, mtpin1 mtpin3 displayed the constitutive shade avoidance responses, such as the elongated petiole, smaller leaf, and increased auxin and chlorophyll content. Therefore, MtPIN1 and MtPIN3 play dual roles in regulation of shadeavoidance response under different environments. Furthermore, these data suggest that PIN3,4,7 and its orthologs have evolved conserved and specific functions among species.

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The GA 20-Oxidase Encoding Gene MSD1 Controls the Main Stem Elongation in Medicago truncatula

Frontiers in Plant Science ◽

10.3389/fpls.2021.709625 ◽

2021 ◽

Vol 12 ◽

Author(s):

Wanying Li ◽

Qingxia Ma ◽

Pengcheng Yin ◽

Jiangqi Wen ◽

Yanxi Pei ◽

...

Keyword(s):

Plant Height ◽

Medicago Truncatula ◽

Crop Production ◽

Molecular Mechanisms ◽

Stem Elongation ◽

Biologically Active ◽

Main Stem ◽

Loss Of Function ◽

Main Shoot ◽

Model Legume

Plant height is an important agronomic trait that is closely related to biomass yield and crop production. Despite legumes comprise one of the largest monophyletic families that are second only to grasses in terms of economic and nutritional values, due to an ancient genome duplication event, most legume plants have complex genomes, thus the molecular mechanisms that determine plant height are less known in legumes. Here, we report the identification and characterization of MAIN STEM DWARF1 (MSD1), which is required for the plant height in the model legume Medicago truncatula. Loss of function of MSD1 leads to severely reduced main stem height but normal lateral branch elongation in M. truncatula. Histological analysis revealed that the msd1-1 main stem has shorter internodes with reduced cell size and number compared with the wild type, indicating that MSD1 affects cell elongation and cell proliferation. MSD1 encodes a putative GA 20-oxidase that is expressed at significantly higher levels in the main shoot apex than in the lateral shoot apices, suggesting that MSD1 expression is associated with its effect on the main stem elongation. UPLC-MS/MS analysis showed that GA9 and GA4, two identified products of the GA 20-oxidase, were severely reduced in msd1-1, and the dwarf phenotype of msd1-1 could be rescued by supplementation with gibberellic acid GA3, confirming that MSD1 functions as a biologically active GA 20-oxidase. Moreover, we found that disruption of either MtGA20ox7 or MtGA20ox8, homologs of MSD1, has little effects on the elongation of the main stem, while the msd1-1 mtga20ox7-1 mtga20ox8 triple mutants exhibits a severe short main shoot and lateral branches, as well as reduced leaf size, suggesting that MSD1 and its homologs MtGA20ox7 and MtGA20ox8, redundantly regulate M. truncatula shoot elongation and leaf development. Taken together, our findings demonstrate the molecular mechanism of MSD1-mediated regulation of main stem elongation in M. truncatula and provide insights into understanding the functional diversity of GA 20-oxidases in optimizing plant architecture in legumes.

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Measuring Auxin Transport Capacity in Seedling Roots of Medicago truncatula

BIO-PROTOCOL ◽

10.21769/bioprotoc.1842 ◽

2016 ◽

Vol 6 (12) ◽

Author(s):

Jason Ng ◽

Ulrike Mathesius

Keyword(s):

Medicago Truncatula ◽

Auxin Transport ◽

Transport Capacity ◽

Seedling Roots

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Does Green Really Mean Go? Increasing the Fraction of Green Photons Promotes Growth of Tomato but Not Lettuce or Cucumber

Plants ◽

10.3390/plants10040637 ◽

2021 ◽

Vol 10 (4) ◽

pp. 637

Author(s):

Paul Kusuma ◽

Boston Swan ◽

Bruce Bugbee

Keyword(s):

Leaf Area ◽

Stem Elongation ◽

Wavelength Region ◽

Sole Source ◽

Dry Mass ◽

Leaf Expansion ◽

Photon Flux ◽

Shade Avoidance ◽

Crop Species ◽

Blue Region

The photon flux in the green wavelength region is relatively enriched in shade and the photon flux in the blue region is selectively filtered. In sole source lighting environments, increasing the fraction of blue typically decreases stem elongation and leaf expansion, and smaller leaves reduce photon capture and yield. Photons in the green region reverse these blue reductions through the photoreceptor cryptochrome in Arabidopsis thaliana, but studies in other species have not consistently shown the benefits of photons in the green region on leaf expansion and growth. Spectral effects can interact with total photon flux. Here, we report the effect of the fraction of photons in the blue (10 to 30%) and green (0 to 50%) regions at photosynthetic photon flux densities of 200 and 500 µmol m−2 s−1 in lettuce, cucumber and tomato. As expected, increasing the fraction of photons in the blue region consistently decreased leaf area and dry mass. By contrast, large changes in the fraction of photons in the green region had minimal effects on leaf area and dry mass in lettuce and cucumber. Photons in the green region were more potent at a lower fraction of photons in the blue region. Photons in the green region increased stem and petiole length in cucumber and tomato, which is a classic shade avoidance response. These results suggest that high-light crop species might respond to the fraction of photons in the green region with either shade tolerance (leaf expansion) or shade avoidance (stem elongation).

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An improved genome release (version Mt4.0) for the model legume Medicago truncatula

BMC Genomics ◽

10.1186/1471-2164-15-312 ◽

2014 ◽

Vol 15 (1) ◽

pp. 312 ◽

Cited By ~ 191

Author(s):

Haibao Tang ◽

Vivek Krishnakumar ◽

Shelby Bidwell ◽

Benjamin Rosen ◽

Agnes Chan ◽

...

Keyword(s):

Medicago Truncatula ◽

Model Legume

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Guidelines for Genetic Nomenclature and Community Governance for the Model Legume Medicago truncatula

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2001.14.12.1364 ◽

2001 ◽

Vol 14 (12) ◽

pp. 1364-1367 ◽

Cited By ~ 14

Author(s):

Kathryn A. VandenBosch ◽

Julia Frugoli

Keyword(s):

Medicago Truncatula ◽

Rapid Growth ◽

Model System ◽

Gene Nomenclature ◽

Community Governance ◽

Model Legume ◽

The Past ◽

Genetic Nomenclature ◽

International Collaborations

At the 2nd Medicago meeting (a satellite of the 1999 IS-MPMI meeting in Amsterdam), investigators perceived a need for standardization of genetic nomenclature in Medicago truncatula, due to the rapid growth of research on this species in the past few years. Establishment of such standards grew out of discussions begun at this meeting and continued electronically throughout the M. truncatula community. The proposed standards presented here are the consensus results of those discussions. In addition to standards for gene nomenclature, a method for community governance and a website for cataloging gene names and submitting new ones are presented. The purpose of implementing these guidelines is to help maintain consistency in the literature, to avoid redundancy, to contribute to the accuracy of databases, and, in general, to aid the international collaborations that have made M. truncatula a model system for legume biology.

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Structure and antimicrobial activity of NCR169, a nodule-specific cysteine-rich peptide of Medicago truncatula

Scientific Reports ◽

10.1038/s41598-021-89485-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Noriyoshi Isozumi ◽

Yuya Masubuchi ◽

Tomohiro Imamura ◽

Masashi Mori ◽

Hironori Koga ◽

...

Keyword(s):

Antimicrobial Activity ◽

Medicago Truncatula ◽

Mechanism Of Action ◽

Disulfide Bonds ◽

Sinorhizobium Meliloti ◽

Bound State ◽

Disulfide Linkage ◽

Model Legume ◽

Nmr Structures ◽

And Function

AbstractA model legume, Medicago truncatula, has over 600 nodule-specific cysteine-rich (NCR) peptides required for symbiosis with rhizobia. Among them, NCR169, an essential factor for establishing symbiosis, has four cysteine residues that are indispensable for its function. However, knowledge of NCR169 structure and mechanism of action is still lacking. In this study, we solved two NMR structures of NCR169 caused by different disulfide linkage patterns. We show that both structures have a consensus C-terminal β-sheet attached to an extended N-terminal region with dissimilar features; one moves widely, whereas the other is relatively stapled. We further revealed that the disulfide bonds of NCR169 contribute to its structural stability and solubility. Regarding the function, one of the NCR169 oxidized forms could bind to negatively charged bacterial phospholipids. Furthermore, the positively charged lysine-rich region of NCR169 may be responsible for its antimicrobial activity against Escherichia coli and Sinorhizobium meliloti. This active region was disordered even in the phospholipid bound state, suggesting that the disordered conformation of this region is key to its function. Morphological observations suggested the mechanism of action of NCR169 on bacteria. The present study on NCR169 provides new insights into the structure and function of NCR peptides.

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A method for the isolation of root hairs from the model legume Medicago truncatula

Journal of Experimental Botany ◽

10.1093/jxb/erg245 ◽

2003 ◽

Vol 54 (391) ◽

pp. 2245-2250 ◽

Cited By ~ 12

Author(s):

J. Ramos

Keyword(s):

Medicago Truncatula ◽

Root Hairs ◽

Model Legume

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Functional specialization of Arf paralogs in nodules of model legume, Medicago truncatula

Plant Growth Regulation ◽

10.1007/s10725-016-0227-2 ◽

2016 ◽

Vol 81 (3) ◽

pp. 501-510 ◽

Cited By ~ 1

Author(s):

Elif Yüzbaşıoğlu ◽

Eda Dalyan ◽

Abdülrezzak Memon ◽

Gül Öz ◽

Bayram Yüksel

Keyword(s):

Medicago Truncatula ◽

Functional Specialization ◽

Model Legume

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Comparison of nodule endophyte composition, diversity, and gene content between Medicago truncatula genotypes

Phytobiomes Journal ◽

10.1094/pbiomes-10-20-0077-r ◽

2021 ◽

Author(s):

Mannix Burns ◽

Brendan Epstein ◽

Liana Burghardt

Keyword(s):

Functional Groups ◽

Medicago Truncatula ◽

Root Nodules ◽

Bacterial Endophytes ◽

Host Genotype ◽

Model Legume ◽

Symbiotic Relationships ◽

Functional Assays ◽

Altered Gene ◽

Significant Direct Effect

Leguminous plants form symbiotic relationships with rhizobia. These nitrogen-fixing bacteria live in specialized root organs called nodules. While rhizobia form the most notable host relationship within root nodules, other bacterial endophytes also inhabit these root nodules and can influence host-rhizobia interactions as well as exert effects of their own, whether beneficial or detrimental. In this study, we investigate differences in nodule communities between genotypes (A17 and R108) of a single plant species, the model legume Medicago truncatula. While diversity of endophytes in nodules was similar across hosts, both nodule endophyte composition and gene functional groups differed. In contrast to the significant direct effect of host genotype, neither the presence nor identity of a host in the previous generation (either A17 or R108) had a significant effect on the nodule endophyte diversity or composition. However, whether or not a host was present altered gene functional groups. We conclude that genetic variation within a legume host species can play an important role in the establishment of nodule microbiomes. Further studies, including GWAS and functional assays, can open the door for engineering and optimizing nodule endophyte communities that promote growth or have other beneficial qualities.

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