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Brachytic2/ZmABCB1 functions in IAA export from intercalary meristems.

Knöller AS, Blakeslee JJ, Richards EL, Peer WA, Murphy AS - J. Exp. Bot. (2010)

Bottom Line: Arabidopsis abcb1 mutants exhibit only minor reductions in auxin transport and plant height unless combined with mutations in the ABCB19 auxin transporter.BR2 is expressed in nodal meristems, and analyses of auxin transport and content indicate that BR2 function in these grass-specific tissues is analogous to ABCB1 function in the shoot and root apex of Arabidopsis.These results indicate that ABCB1/BR2 function is conserved between dicots and monocots, but also suggests that this function must be understood in the context of the segmental organization of grass plants.

View Article: PubMed Central - PubMed

Affiliation: Purdue University, Horticulture and Landscape Architecture Department, 625 Agriculture Mall Drive, West Lafayette, IN 47907, USA.

ABSTRACT
Dwarfism traits in Zea mays are regulated by multiple factors including the hormone auxin. Dwarf brachytic2 (br2) mutants harbour lesions in the gene encoding an orthologue of Arabidopsis thaliana ABCB1 which functions in auxin efflux out of meristematic regions in the shoot and root. br2 mesocotyls and coleoptiles exhibit reduced auxin transport. However, the dwarf stature of br2 derives from shortened lower internodes whilst the upper portion of the plant is completely normal. As such, it is counter-intuitive to attribute br2 dwarfism exclusively to reduced auxin export out of the shoot apex. Arabidopsis abcb1 mutants exhibit only minor reductions in auxin transport and plant height unless combined with mutations in the ABCB19 auxin transporter. Phylogenetic modelling analysis excludes the possibility that BR2 is more closely related to ABCB19 which has three more closely related orthologues in maize. BR2 is expressed in nodal meristems, and analyses of auxin transport and content indicate that BR2 function in these grass-specific tissues is analogous to ABCB1 function in the shoot and root apex of Arabidopsis. These results indicate that ABCB1/BR2 function is conserved between dicots and monocots, but also suggests that this function must be understood in the context of the segmental organization of grass plants.

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Related in: MedlinePlus

Model for internode elongation in monocots. Auxin and gibberellic acid (GA) interact during cellular elongation. Both auxin and gibberellic acid promote the reorientation of microtubules (MT) from random to transverse, and suppress cell wall peroxidase activity, thereby promoting cell wall extensibility. (This figure is available in colour at JXB online.)
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fig1: Model for internode elongation in monocots. Auxin and gibberellic acid (GA) interact during cellular elongation. Both auxin and gibberellic acid promote the reorientation of microtubules (MT) from random to transverse, and suppress cell wall peroxidase activity, thereby promoting cell wall extensibility. (This figure is available in colour at JXB online.)

Mentions: Dwarfism traits have been particularly beneficial for crop production, and the introduction of dwarf varieties of wheat and rice served as a cornerstone of the ‘Green Revolution’ of the late 20th century. During this period, the generation of high-yield varieties significantly increased cereal production, especially in Latin America and India (Gaud, 1968). High-yield varieties have higher nitrogen uptake capacities and exhibit increased overall growth and cell elongation. However, taller plants are more likely to lodge in response to heavy rainfall and wind, and the heavier inflorescences of high-yield elite breeds make them more susceptible to lodging. To ameliorate this negative characteristic, dwarf and semi-dwarf traits were identified and subsequently bred into these high-yield lines (Gale and Youssefian, 1985; Salamini, 2003). The most useful dwarfing traits are associated with defects in the biosynthesis or perception of the growth hormone gibberellic acid, or GA (Fig. 1; Peng et al., 1999; Monna et al., 2002). However, manipulation of GA biosynthesis and signal transduction has been a less effective strategy in Zea mays and Sorghum bicolor, as GA mutants in these species generally exhibit defects in the reproductive organs (Evans and Poethig, 1995; Miralles et al., 1998).


Brachytic2/ZmABCB1 functions in IAA export from intercalary meristems.

Knöller AS, Blakeslee JJ, Richards EL, Peer WA, Murphy AS - J. Exp. Bot. (2010)

Model for internode elongation in monocots. Auxin and gibberellic acid (GA) interact during cellular elongation. Both auxin and gibberellic acid promote the reorientation of microtubules (MT) from random to transverse, and suppress cell wall peroxidase activity, thereby promoting cell wall extensibility. (This figure is available in colour at JXB online.)
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2921204&req=5

fig1: Model for internode elongation in monocots. Auxin and gibberellic acid (GA) interact during cellular elongation. Both auxin and gibberellic acid promote the reorientation of microtubules (MT) from random to transverse, and suppress cell wall peroxidase activity, thereby promoting cell wall extensibility. (This figure is available in colour at JXB online.)
Mentions: Dwarfism traits have been particularly beneficial for crop production, and the introduction of dwarf varieties of wheat and rice served as a cornerstone of the ‘Green Revolution’ of the late 20th century. During this period, the generation of high-yield varieties significantly increased cereal production, especially in Latin America and India (Gaud, 1968). High-yield varieties have higher nitrogen uptake capacities and exhibit increased overall growth and cell elongation. However, taller plants are more likely to lodge in response to heavy rainfall and wind, and the heavier inflorescences of high-yield elite breeds make them more susceptible to lodging. To ameliorate this negative characteristic, dwarf and semi-dwarf traits were identified and subsequently bred into these high-yield lines (Gale and Youssefian, 1985; Salamini, 2003). The most useful dwarfing traits are associated with defects in the biosynthesis or perception of the growth hormone gibberellic acid, or GA (Fig. 1; Peng et al., 1999; Monna et al., 2002). However, manipulation of GA biosynthesis and signal transduction has been a less effective strategy in Zea mays and Sorghum bicolor, as GA mutants in these species generally exhibit defects in the reproductive organs (Evans and Poethig, 1995; Miralles et al., 1998).

Bottom Line: Arabidopsis abcb1 mutants exhibit only minor reductions in auxin transport and plant height unless combined with mutations in the ABCB19 auxin transporter.BR2 is expressed in nodal meristems, and analyses of auxin transport and content indicate that BR2 function in these grass-specific tissues is analogous to ABCB1 function in the shoot and root apex of Arabidopsis.These results indicate that ABCB1/BR2 function is conserved between dicots and monocots, but also suggests that this function must be understood in the context of the segmental organization of grass plants.

View Article: PubMed Central - PubMed

Affiliation: Purdue University, Horticulture and Landscape Architecture Department, 625 Agriculture Mall Drive, West Lafayette, IN 47907, USA.

ABSTRACT
Dwarfism traits in Zea mays are regulated by multiple factors including the hormone auxin. Dwarf brachytic2 (br2) mutants harbour lesions in the gene encoding an orthologue of Arabidopsis thaliana ABCB1 which functions in auxin efflux out of meristematic regions in the shoot and root. br2 mesocotyls and coleoptiles exhibit reduced auxin transport. However, the dwarf stature of br2 derives from shortened lower internodes whilst the upper portion of the plant is completely normal. As such, it is counter-intuitive to attribute br2 dwarfism exclusively to reduced auxin export out of the shoot apex. Arabidopsis abcb1 mutants exhibit only minor reductions in auxin transport and plant height unless combined with mutations in the ABCB19 auxin transporter. Phylogenetic modelling analysis excludes the possibility that BR2 is more closely related to ABCB19 which has three more closely related orthologues in maize. BR2 is expressed in nodal meristems, and analyses of auxin transport and content indicate that BR2 function in these grass-specific tissues is analogous to ABCB1 function in the shoot and root apex of Arabidopsis. These results indicate that ABCB1/BR2 function is conserved between dicots and monocots, but also suggests that this function must be understood in the context of the segmental organization of grass plants.

Show MeSH
Related in: MedlinePlus