Short catkin1, a novel mutant of Castanea mollissima, is associated with programmed cell death during chestnut staminate flower differentiation

The fact that male flowers far outnumber female flowers is a factor that limits nut yield in Chinese chestnut. A naturally occurring mutation of male catkins was found on a single branch of a Chinese chestnut tree in the mountains near Beijing, China. The mutation was named short catkin1 (sck1). The catkin length of sck1 was only 1/6 to 1/8 that of the wild-type male catkins on the same tree. The mutation was associated with a greater number of female flowers and increased yield. Observations on the development of male catkins with the sck1 phenotype showed that the distal part of the catkins aborted at the stage of chestnut staminate flower differentiation. Further research using transmission electron microscope analysis showed that the process of cell death in sck1 catkins had the typical characteristics of programmed cell death at the subcellular level, such as condensed chromatin, dissolved nucleolus, degraded karyoplasm, burst karyotheca, and disintegrated chloroplasts or mitochondria. Significantly, DNA laddering was detected in tissues of sck1 catkins. In conclusion, the results showed that sck1 was associated with PCD.

► A natural short-catkin mutation of Chinese chestnut was found in Beijing, China.
► Its catkin is only 1/6 to 1/8 short in length of common chestnut.
► We observed the developmental processes of its catkins by TEM and paraffin method, and detected its DNA.
► The trait assays have provided evidences that programmed cell death leads to the short-catkin happened.