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See detailArchitectural and developmental changes due to overexpression of the JOINTLESS gene in tomato
Huerga Fernandez, Samuel ULiege; Orman-Ligeza, Beata; Périlleux, Claire ULiege

Poster (2019, June)

Inflorescence architecture shows huge variation among flowering plants, especially in the amount of flowers and branching degree. In tomato, the formation of the inflorescence follows a sympodial pattern ... [more ▼]

Inflorescence architecture shows huge variation among flowering plants, especially in the amount of flowers and branching degree. In tomato, the formation of the inflorescence follows a sympodial pattern : the shoot apical meristem (SAM) acquires a floral meristem (FM) fate and forms the first flower while a lateral inflorescence meristem (IM) is initiated, which itself matures into a FM when a second IM is initiated, and so on. This sympodial mode of inflorescence development is regulated by a complex genetic network, which remains to be elucidated. Tomato is also used as a model in the study of abscission, an important process by which plants can isolate and drop different parts such as non fertilized flowers, damaged organs or ripe fruits. The lack of fruit abscission zone – the “jointless” phenotype – is associated with the j and j-2 mutations, which impair the function of two MADS-box genes: JOINTLESS (J) and SlMBP21. We are interested in understanding the functions of J, because j knock-out mutation does not only alter the abscission zone but causes inflorescence reversion to leaf production after the initiation of few flowers. Our goal is therefore to identify the targets of J by different molecular approaches. [less ▲]

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See detailOverexpression of the tomato JOINTLESS gene alters flowering
Huerga Fernandez, Samuel ULiege; Orman-Ligeza, Beata; Goossens, Chiara ULiege et al

Poster (2018, May 17)

Abscission is an important mechanism that allows plants to separate unfertilized flowers, ripe fruits or damage organs from the plant. In tomato, jointless (j) and jointless-2 (j-2) mutations leads a lack ... [more ▼]

Abscission is an important mechanism that allows plants to separate unfertilized flowers, ripe fruits or damage organs from the plant. In tomato, jointless (j) and jointless-2 (j-2) mutations leads a lack of abscission zone (AZ) in the flower pedicel, which will avoid falling of ripe fruits and prevent loss of yield. Both J and J-2 are genes encoding MADS-box transcription factors (Mao et al. 2000; Gomez-Roldan et al., 2017) that can interact with other MADS-box proteins, like MACROCALYX (MC), forming a multimeric complex able to regulate the AZ formation (Liu et al. 2014). In addition to the AZ formation, J also plays a role in flowering architecture and meristem fate. This last role is consistent with the functions of the closets homologs of J in Arabidopsis, SHORT VEGETATIVE PHASE (SVP) and AGAMOUS LIKE 24 (AGL24) (Gregis et al. 2006). Mutation of J leads to a faster flower maturation and a reversion to the vegetative state of the inflorescence meristems, which originates leafy inflorescences (Périlleux et al. 2014). Nevertheless, J is not the only one that regulates at the same time AZ formation and meristem functions. Other transcription factors such as the tomato homolog of WUSHEL (LeWUS), GOBLET (GOB), LATERAL SUPPRESSOR (Ls) and Blind (Bl) are involved in those pathways (Nakano et al. 2012; Nakano et al. 2013). We have generated transgenic plants that overexpress J (35S:J) showing changes in the inflorescence architecture and AZ development, but also having interesting phenotypes in axillary development and leaf complexity. These results suggest that J takes part in different pathways and regulate several downstream genes. Our goal is to identify and study the targets of the J transcription factor in order to understand its functions in the tomato plant. [less ▲]

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See detailTowards understanding the function of JOINTLESS gene in tomato inflorescence
Huerga Fernandez, Samuel ULiege; Gómez Roldán, Maria Victoria; Orman-Ligeza, Beata ULiege et al

Poster (2017, September)

The lack of fruit abscission is a trait of great agronomical value. In tomato, the jointless phenotype, referring to the lack of abscission zone (AZ) in the flower pedicel, has been obtained by two ... [more ▼]

The lack of fruit abscission is a trait of great agronomical value. In tomato, the jointless phenotype, referring to the lack of abscission zone (AZ) in the flower pedicel, has been obtained by two independent mutations, named jointless (j) and jointless-2 (j-2). The corresponding genes encode MADS-box transcription factors, as shown in 2000 for J (Mao et al. 2000) and very recently for J-2, known as SlMBP21 (Gomez-Roldan et al., 2017). Similar to the quartet model of MADS-box protein complexes regulating floral organ formation, J and J-2 interact with MADS-box partners, among which MACROCRALYX (MC), to regulate AZ formation (Liu et al. 2014). In addition to - or in connection with - AZ formation, J acts during the building of the inflorescence to regulate meristem fate. Indeed j mutants produce leafy inflorescences characterized by faster flower maturation and resumption of vegetative meristems (Périlleux et al. 2014). For these traits, j is epistatic to j-2. The involvement of J in the regulation of meristem fate is consistent with the roles of its closest homologs in Arabidopsis, AGAMOUS LIKE 24 (AGL24) and SHORT VEGETATIVE PHASE (SVP). Our goal is to identify J targets in order to unravel its multiple functions in the tomato inflorescence. [less ▲]

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See detailNatural and induced loss of function mutations in SlMBP21 MADS-box gene led to jointless-2 phenotype in tomato
Gomez Roldan, Maria Victoria; Périlleux, Claire ULiege; Morin, Halima et al

in Scientific Reports (2017), 7

Abscission is the mechanism by which plants disconnect unfertilized flowers, ripe fruits, senescent or diseased organs from the plant. In tomato, pedicel abscission is an important agronomic factor that ... [more ▼]

Abscission is the mechanism by which plants disconnect unfertilized flowers, ripe fruits, senescent or diseased organs from the plant. In tomato, pedicel abscission is an important agronomic factor that controls yield and post-harvest fruit quality. Two non-allelic mutations, jointless (j) and jointless-2 (j-2), controlling pedicel abscission zone formation have been documented but only j-2 has been extensively used in breeding. J was shown to encode a MADS-box protein. Using a combination of physical mapping and gene expression analysis we identified a positional candidate, Solyc12g038510, associated with j-2 phenotype. Targeted knockout of Solyc12g038510, using CRISPR/Cas9 system, validated our hypothesis. Solyc12g038510 encodes the MADS-box protein SlMBP21. Molecular analysis of j-2 natural variation revealed two independent loss-of-function mutants. The first results of an insertion of a Rider retrotransposable element. The second results of a stop codon mutation that leads to a truncated protein form. To bring new insights into the role of J and J-2 in abscission zone formation, we phenotyped the single and the double mutants and the engineered alleles. We showed that J is epistatic to J-2 and that the branched inflorescences and the leafy sepals observed in accessions harboring j-2 alleles are likely the consequences of linkage drags. [less ▲]

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