The NIMA-related kinases (NEKs) are a family of serine/threonine kinases largely involved in cell cycle control in fungi, mammals and other eukaryotes. In Arabidopsis, NEK6 is involved in the regulation of epidermal cell morphogenesis. However, other roles of NEK6 in plants are less understood. Here we report functions of NEK6 in plant growth, development and stress responses in Arabidopsis. NEK6 transcripts and proteins are induced by ethylene precursor ACC and salt stress. Expressions of other NEK genes except NEK5 are also responsive to the two treatments. Overexpression and mutant analysis disclose that NEK6 gene increases rosette growth, seed yield and lateral root formation. However, NEK6 appears to play a negative role in control of seed size. The gene also promotes plant tolerance to salt stress and osmotic stress in its overexpressing plants. NEK6 gene may achieve its functions through suppression of ethylene biosynthesis and activation of CYCB1;1 and CYCA3;1 expression. Our present study reveals new functions of NEK6 gene in plant growth and stress tolerance, and manipulation of the NEK6 may improve important agronomic traits in crop plants.

Keywords:
Arabidopsis;NIMA-related kinase;organ size;abiotic stress;CYCB1;1;ethylene