Identification and functional study of a mild allele of SlDELLA gene conferring the potential for improved yield in tomato

Abstract

Parthenocarpy, or pollination-independent fruit set, is an attractive trait for fruit production and can be induced by increased responses to the phytohormone gibberellin (GA), which regulates diverse aspects of plant development. GA signaling in plants is negatively regulated by DELLA proteins. A loss-of-function mutant of tomato DELLA (SlDELLA), procera (pro) thus exhibits enhanced GA-response phenotypes including parthenocarpy, although the pro mutation also confers some disadvantages for practical breeding. This study identified a new milder hypomorphic allele of SlDELLA, procera-2 (pro-2), which showed weaker GA-response phenotypes than pro. The pro-2 mutant contains a single nucleotide substitution, corresponding to a single amino acid substitution in the SAW subdomain of the SlDELLA. Accumulation of the mutated SlDELLA transcripts in wild-type (WT) resulted in parthenocarpy, while introduction of intact SlDELLA into pro-2 rescued mutant phenotypes. Yeast two-hybrid assays revealed that SlDELLA interacted with three tomato homologues of GID1 GA receptors with increasing affinity upon GA treatment, while their interactions were reduced by the pro and pro-2 mutations. Both pro and pro-2 mutants produced higher fruit yields under high temperature conditions, which were resulted from higher fruit set efficiency, demonstrating the potential for genetic parthenocarpy to improve yield under adverse environmental conditions.

Tomato Fruit Development and Metabolism

“…Consistent with this, the silencing of the SlDELLA gene in tomato resulted in small, facultative parthenocarpic fruits with an elongated shape (Martí et al, 2007). The procera ( pro ) mutant, which carries a point mutation in the GRAS region of SlDELLA , has also very strong parthenocarpic capacity and shows enhanced growth of preanthesis ovaries (Jones, 1987; Carrera et al, 2012; Shinozaki et al, 2018c). The parthenocarpic capacity of pro is mainly associated with changes in the expression of genes involved in GA and auxin pathways (Carrera et al, 2012).…”

“…The parthenocarpic capacity of pro is mainly associated with changes in the expression of genes involved in GA and auxin pathways (Carrera et al, 2012). A new SlDELLA mutant containing a single nucleotide substitution, procera2 ( pro2 ), has been recently identified and shows a potential for high fruit yield in both optimal and unfavorable growing conditions due to its facultative parthenocarpic capacity (Shinozaki et al, 2018c). Parthenocarpy is indeed an attractive trait for fruit production (Shinozaki et al, 2018c).…”

Loss-of-Function of a Tomato Receptor-Like Kinase Impairs Male Fertility and Induces Parthenocarpic Fruit Set

“…In conclusion, this study identified a novel tomato mutant showing parthenocarpy and this was caused by the loss of function in the gene encoding a receptor kinase gene designated as SPFF . The parthenocarpic variety potentially shows improved fruit productivity due to increased fruit set efficiency (Shinozaki et al, 2018a), although the spff produced delayed growth, smaller mature fruits and reduced yield compared to WT (Figure 5). Such unfavorable traits render this mutant less attractive for breeding application, but it would be interesting to identify hypomorphic (weaker) alleles of spff carrying less detrimental phenotypes through screening from TILLING populations or genome editing approaches (Okabe et al, 2011; Shimatani et al, 2017), and investigate their potentials for impact on breeding application.…”

Functional Disruption of the Tomato Putative Ortholog of HAWAIIAN SKIRT Results in Facultative Parthenocarpy, Reduced Fertility and Leaf Morphological Defects

“…Increase in Brix value has been reported in some parthenocarpic tomato lines (Carmi et al, 2003; Medina et al, 2013). Higher Brix index and lycopene content have also been reported in the procera-2 parthenocarpic mutant, a novel allele of SlDELLA (Shinozaki et al, 2018).…”