CsKTN1 for a katanin p60 subunit is associated with the regulation of fruit elongation in cucumber (Cucumis sativus L.)

Authors: HUL, WANG - Northwest A&f University; JING, SUN - Northwest A&f University; FANG, YANG - Northwest A&f University; Weng, Yiqun; PENG, CHEN - Northwest A&f University; SHENLI, DU - Tianjin Agricultural University; AIMING, WEL - Tianjin Agricultural University; YUHONG, LI - Northwest A&f University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2021
Publication Date: 5/27/2021
Citation: Hul, W., Jing, S., Fang, Y., Weng, Y., Peng, C., Shenli, D., Aiming, W., Yuhong, L. 2021. CsKTN1 for a katanin p60 subunit is associated with the regulation of fruit elongation in cucumber (Cucumis sativus L.). Theoretical and Applied Genetics. 134:2429-2441. https://doi.org/10.1007/s00122-021-03833-y.
DOI: https://doi.org/10.1007/s00122-021-03833-y

Interpretive Summary: In cucumber production, fruit length is an important attribute for fruit yield and quality, but little is known on the molecular mechanisms of fruit growth in cucumber. In this study, we identified and characterized a cucumber 'short fruit' mutant. Microscopic observation found that the shorter fruit in the mutant was due to the reduced cell numbers. Genetic analysis revealed a single gene is underlying the mutant appearance with semi-dominance. We cloned this gene, and show that the it was a homolog of KTN1 (CsKTN1) that codes for a katanin p60 subunit. The mutant phenotype is due to single nucleotide mutation in the coding region of the CsKTN1 gene. There was no significant difference in CsKTN1 expression levels between the normal and mutant plants. We measured plant hormones and examined transcriptomes in the mutant and normal plants. The results suggested that auxin and gibberellin contents were reduced in the mutant due to changes of expression levels of genes related with auxin and gibberellin metabolism and signaling. This work helps understand the function of the katanin and the molecular mechanisms of fruit growth regulation in cucumber. This work also provides useful information on cucumber improvement.

Technical Abstract: Fruit length is an important horticultural trait for both fruit yield and quality of cucumber (Cucumis sativus L.). Knowledge on the molecular regulation of fruit elongation in cucumber is very limited. In this study, we identified and characterized a cucumber short fruit 3 (sf3) mutant. Histological examination indicated that the shorter fruit in the mutant was due to the reduced cell numbers. Genetic analysis revealed that the phenotype of the sf3 mutant was monogenic semi-dominant inheritance. By map-based cloning and Arabidopsis genetic transformation, we showed that SF3 was a homolog of KTN1 (CsKTN1) encoding a katanin p60 subunit. A non-synonymous mutation in the fifth exon of CsKTN1 resulted in an amino acid substitution from Serine in the wild type to Phenylalanine in the sf3 mutant. CsKTN1 expressed in all tissues of both the wild type and the sf3 mutant. However, there was no significant difference in CsKTN1 expression levels between the wild type and the sf3 mutant. The hormones measurement and RNA-seq analysis suggested that auxin and gibberellin contents were decreased in sf3 by changing the expression levels of genes related with auxin and gibberellin metabolism and signaling. This work helps understand the function of the katanin and the molecular mechanisms of fruit growth regulation in cucumber.