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.

中文翻译：

---

SlMBP21 MADS-box基因中自然和诱导的功能突变丧失导致番茄的lessless-2表型。

脱落是植物断开未受精花，成熟果实，衰老或患病器官的机制。在番茄中，花梗脱落是控制产量和收获后果实品质的重要农艺因素。记录了控制花梗脱落区形成的两个非等位基因突变，无节（j）和无节2（j-2），但只有j-2被广泛用于育种。已显示J编码MADS-box蛋白。结合物理作图和基因表达分析，我们确定了与j-2表型相关的位置候选Solyc12g038510。使用CRISPR / Cas9系统有针对性地敲除Solyc12g038510，验证了我们的假设。Solyc12g038510编码MADS-box蛋白SlMBP21。对j-2自然变异的分子分析揭示了两个独立的功能丧失突变体。插入Rider可逆转座元件的第一个结果。终止密码子突变的第二个结果导致截短的蛋白质形式。为了给J和J-2在脱落区形成中的作用带来新见解，我们对单突变体和双突变体以及工程等位基因进行了表型分析。我们表明，J对J-2具有上位性，在带有j-2等位基因的种质中观察到的分支花序和多叶萼片很可能是连锁拖曳的结果。我们将单突变体和双突变体以及工程等位基因表型化。我们表明，J对J-2具有上位性，在带有j-2等位基因的种质中观察到的分支花序和多叶萼片很可能是连锁拖曳的结果。我们将单突变体和双突变体以及工程等位基因表型化。我们表明，J对J-2具有上位性，在带有j-2等位基因的种质中观察到的分支花序和多叶萼片很可能是连锁拖曳的结果。