Overexpression of a serine carboxypeptidase increases carpel number and seed production in Arabidopsis thaliana

Seed production is an ultimate component of crop yield. Increasing seed production has long been a pursuit for crop breeders and is an indisputable measure of food safety. Advances in biotechnology can provide novel means to achieve increased seed production by genetic engineering. Overexpression of ECS1 (Extra Carpels and Seeds), a gene encoding a serine carboxypeptidase, partially suppresses the leaf phenotypes of mutant bri1-5, a weak allele of brassinosteroid-insensitive 1 (BRI1). Moreover, overexpression of ECS1 increases the number of carpels and seeds per fruit (silique) in Arabidopsis thaliana. Most of the ECS1-overexpressing lines have three-carpel siliques instead of two-carpel siliques found in wild type, while some even have four-carpel siliques. Wildtype plants have an average seed number of 66.2 +/- 3.6 per silique, whereas ECS1-overexpressing lines contain 88.1 +/- 4.1 seeds per silique. The total seed weight per silique increases by about 33% in ECS1-overexpressing plants due to the increased total number of seeds. In addition, ECS1 overexpression enhances the multi-carpel phenotypes in clavata3-2 and causes severely fasciated stems in det2 mutants. To the best of our knowledge, it has not been previously shown that overexpressions of genes that encode serine carboxypeptidases are implicated in reproductive development or produce an increased carpel and seed numbers in any plant species.