Evidence that auxin is required for normal seed size and starch synthesis in pea

McAdam, Erin L.; Meitzel, Tobias; Quittenden, Laura J.; Davidson, Sandra E.; Dalmais, Marion; Bendahmane, Abdelhafid; Thompson, Richard J.; Smith, Jennifer J.; Nichols, David S.; Urquhart, Shelley; Gélinas-Marion, Ariane; Aubert, Grégoire; Ross, John J.

doi:10.1111/nph.14690

Cited by 63 publications

(55 citation statements)

References 61 publications

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“…Our results show that in addition to its function in the response to the perceived gravity signal, auxin is also essential for regulating starch granule accumulation in the root apex and gravity perception (Fig. ), as well as in the seeds of pea as previously reported (McAdam et al ., ). Thus, we propose that auxin has a dual role in root gravitropism.…”

Section: Discussionmentioning

confidence: 97%

Auxin‐mediated statolith production for root gravitropism

Zhang

Xiao

et al. 2019

New Phytologist

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Summary Root gravitropism is one of the most important processes allowing plant adaptation to the land environment. Auxin plays a central role in mediating root gravitropism, but how auxin contributes to gravitational perception and the subsequent response are still unclear. Here, we showed that the local auxin maximum/gradient within the root apex, which is generated by the PIN directional auxin transporters, regulates the expression of three key starch granule synthesis genes, SS4, PGM and ADG1, which in turn influence the accumulation of starch granules that serve as a statolith perceiving gravity. Moreover, using the cvxIAA‐ccvTIR1 system, we also showed that TIR1‐mediated auxin signaling is required for starch granule formation and gravitropic response within root tips. In addition, axr3 mutants showed reduced auxin‐mediated starch granule accumulation and disruption of gravitropism within the root apex. Our results indicate that auxin‐mediated statolith production relies on the TIR1/AFB‐AXR3‐mediated auxin signaling pathway. In summary, we propose a dual role for auxin in gravitropism: the regulation of both gravity perception and response.

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Section: Discussionmentioning

confidence: 97%

Auxin‐mediated statolith production for root gravitropism

Zhang

Xiao

et al. 2019

New Phytologist

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“…Until now, the underlying mechanism by which T6P integrates carbohydrate partitioning with the hormonal control of plant development has not been apparent. Importantly, our data now indicate that auxin is a key factor in mediating the effects of T6P, which acts upstream of the pivotal auxin biosynthesis gene TAR2 (McAdam et al, 2017) to trigger seed filling in pea. We propose that this process is mediated via a modulation of the auxin 4-Cl-IAA (Figure 5), the concentration of which increases sharply at the transition stage (Tivendale et al, 2012).…”

Section: Discussionmentioning

confidence: 63%

“…In pea, TAR2 participates in auxin biosynthesis via the indole-3-pyruvic acid pathway, and mutation of the corresponding gene leads to reduced levels of 4-chloro-indole-3-acetic acid (4-Cl-IAA), the predominant auxin in maturing seeds (Tivendale et al, 2012). Remarkably, the tar2-1 mutation affects the phase transition into seed filling, resulting in the formation of small, wrinkled seeds with decreased starch content and a considerably lower level of AGP activity (McAdam et al, 2017). Our finding that USP::TPP seeds phenocopied those of the tar2-1 mutant, and that introduction of USP::TPP into a tar2-1 background had no additional phenotypic effects beyond those of the parental lines (Table 1, experiment 1 and Figure 3B), raises the possibility that both T6P and TAR2 act in the same signaling pathway.…”

Section: Resultsmentioning

confidence: 99%

“…As proof of this, we created hybrids between USP::TPP plants and transgenic plant lines harboring the USP::TAR2 transgene, which directs expression of the TAR2 coding sequence under the control of the embryo-specific USP promoter. To generate combinations of both transgenes, two previously generated USP::TAR2 lines #3 and #5 (McAdam et al, 2017) were crossed with USP::TPP #2 and #3 plants (Table 1, experiment 2). Segregants from these crosses were used to establish three double transgene homozygotes, referred to as USP::TPP #2/ USP::TAR2 #3, USP::TPP #3/ USP::TAR2 #3 and USP::TPP #3/ USP::TAR2 #5.…”

Section: Resultsmentioning

confidence: 99%

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Trehalose 6-phosphate Controls Seed Filling by Inducing Auxin Biosynthesis

Meitzel

Radchuk

McAdam

et al. 2019

Preprint

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24Plants undergo several developmental transitions during their life cycle. One of these, the 25 differentiation of the young embryo from a meristem-like structure into a highly-specialized 26 storage organ, is vital to the formation of a viable seed. For crops in which the seed itself is the 27 end product, effective accumulation of storage compounds is of economic relevance, defining 28 the quantity and nutritive value of the harvest yield. However, the regulatory networks 29 underpinning the phase transition into seed filling are poorly understood. Here we show that 30 trehalose 6-phosphate (T6P), which functions as a signal for sucrose availability in plants, 31 mediates seed filling processes in seeds of the garden pea (Pisum sativum), a key grain legume. 32Seeds deficient in T6P are compromised in size and starch production, resembling the wrinkled 33 seeds studied by Gregor Mendel. We show also that T6P exerts these effects by stimulating the 34 biosynthesis of the pivotal plant hormone, auxin. We found that T6P promotes the expression 35 of the auxin biosynthesis gene TRYPTOPHAN AMINOTRANSFERASE RELATED2 (TAR2), 36 and the resulting effect on auxin levels is required to mediate the T6P-induced activation of 37 storage processes. Our results suggest that auxin acts downstream of T6P to facilitate seed 38 filling, thereby providing a salient example of how a metabolic signal governs the hormonal 39 control of an integral phase transition in a crop plant.40 41 Keywords 42 Trehalose 6-phosphate, auxin, sugar signaling, embryo development, seed filling, starch 43 biosynthesis, pea 44 45 Introduction 46 The transition from early patterning into seed filling is an important phase change in developing 47 seeds, ensuring seed survival and the nourishment of seedling growth upon germination. For 48 this reason, plants have evolved a regulatory network to control seed filling, and carbohydrates 49 appear to play a pivotal role in this process (Weber et al., 2005; Hills, 2004). Sucrose is thought 50 to have a dual function in developing seeds as a nutrient sugar and as a signal molecule 51 triggering storage-associated gene expression (Weber et al., 1998). Two decades ago, the 52 invertase control hypothesis of seed development was formulated, suggesting that seed coat-53 borne invertases prevent the onset of storage processes in the early embryo by cleaving the 54 incoming sucrose into hexoses (Weber et al., 1995a). When invertase activity declines, sucrose 55 levels begin to rise and seed filling is initiated. However, relatively little is known about the 56 perception and signaling of this metabolic switch. 57 T6P, the intermediate of trehalose biosynthesis, has been shown to be an essential signal 58 metabolite in plants, linking growth and development to carbon metabolism (Lunn et al., 2006; 59 Figueroa et al., 2016b). The sucrose-T6P nexus model postulates that T6P acts as a signal of 60 sucrose availability, helping to maintain sucrose levels within a range that is appropriate for the 61 developmental st...

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“…The mutant of TAR2 , which is an IAA biosynthesis gene, induces the formation of small seeds with reduced starch content and a wrinkled phenotype at the dry stage. Application of the synthetic auxin 2,4-D partially reversed the wrinkled phenotype but did not restore the starch content of the mutant seeds to that of the WT (McAdam et al, 2017). Our results showed considerable differences in the dynamics of the endogenous hormone levels in the grains during grain filling, and the endogenous ABA and IAA levels were positively related to grain filling during the entire grain-filling stage (Fig.…”

Section: Discussionmentioning

confidence: 92%

The rice G protein γ subunit qPE9-1 positively regulates grain-filling process by interacting with abscisic acid and auxin

Zhang

Zhou

et al. 2018

Preprint

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24The rice genome contains a single G α (RGA1) and G β (RGB1) and five G γ subunits. Recent 25 genetic studies have shown that DEP1/qPE9-1, an atypical putative G γ protein, is responsible 26 for dense and erect panicles, but the biochemical and molecular mechanisms underlying 27 control of grain size are not well understood. Here, we report that plants carrying qPE9-1 28 have more endosperm cells per grain than plants contain the qpe9-1 allele. The qPE9-1 line 29 has a higher rate and longer period of starch accumulation than the qpe9-1 line. Additionally, 30 the expression of several key genes encoding enzymes catalyzing sucrose metabolism and 31 starch biosynthesis is higher in the qPE9-1 line than in the qpe9-1 line, especially from the 32 mid to late grain-filling stage. Grains of the qPE9-1 line also have higher contents of two 33 phytohormones, ABA and IAA. Exogenous application of ABA or IAA enhanced starch 34 accumulation and the expression of genes encoding grain-filling-related enzymes in the 35 grains of qPE9-1, whereas only IAA produced these effects in qpe9-1. Based on these results, 36we conclude that qPE9-1 promotes endosperm cell proliferation and positively regulates 37 starch accumulation largely through ABA and IAA, which enhance the expression of genes 38 encoding starch biosynthesis during the late grain-filling stage. 39 40

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Evidence that auxin is required for normal seed size and starch synthesis in pea

Cited by 63 publications

References 61 publications

Auxin‐mediated statolith production for root gravitropism

Auxin‐mediated statolith production for root gravitropism

Trehalose 6-phosphate Controls Seed Filling by Inducing Auxin Biosynthesis

The rice G protein γ subunit qPE9-1 positively regulates grain-filling process by interacting with abscisic acid and auxin

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