A mutation in <i>CsKTN1</i> for the Katanin p60 protein results in miniature plant in cucumber, <i>Cucumis sativus</i> L.

Katanin, a microtubule shearing protein, plays an important role in plant architecture formation. However, little is known about its mechanisms in regulating plant architecture in cucumber. In the present study, through EMS mutagenesis, we identified a novel micro-plant (mp) mutant in the North China type inbred line CCMC that may be of value for cucumber breeding. The size and number of stem cells were altered in the mp mutant. Through bulked segregant analysis (BSA) sequencing approach combined with genetic mapping, the mp locus was delimited to an interval of 130.9-kb. Multiple lines of evidence suggested that the mp mutation is due to a single nucleotide polymorphism in Csa7G435510 that is predicted to encode the Katanin p60 subunit protein (CsKTN1). The expression levels of CsKTN1 decreased significantly in all tissues except the tendril of mp mutant. Subcellular localization showed that both wild-type and mutant CsKTN1 proteins were located in cell membrane, cytoplasm and nucleus of tobacco leaf cells. The mutant protein lost part of its ability to bind and shear microtubule in vitro. These findings provide new insight into the regulatory function of microtubule-shearing protein, Katanin p60, in plant architecture of cucumber.