Cyclin-dependent kinase involved in pre-mRNA splicing. Required for the correct splicing of the sixth intron of CALS5 pre-mRNA. May stabilize the binding of U1 snRNP to this rare type of intron with a GC 5'SS. Involved in chromosome pairing and is required for the completion of synapsis in male meiocytes at high ambient temperatures. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Forms a complex with CYCL1-1. Associated with the spliceosome. Interacts with RS2Z33. Expressed in leaves and inflorescences. Lower levels of expression in roots and stems. Aberrant callose deposition, defective pollen wall formation during microspore development, and severely reduced male fertility. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.