The genetic basis of plant reproductive organ size is poorly understood. Dr. Chaoying He’s group found that the expression levels of the gene Physalis Organ Size1 (POS1) were positively associated with size variation in Physalis philadelphica (tomatillo) reproductive organs such flowers, berries and seeds. POS1 knockdown resulted in smaller flowers and berries with smaller cells as compared to their wild type counterparts. Conversely, POS1 overexpression promoted organ size without increasing the cell number. The first introns of the POS1 alleles from the large, intermediate and small tomatillo groups contained one, two and three 37-bp repeats, respectively. Furthermore, copy variation of repeats in the first intron of POS1 alleles resulted in differential expression of this gene. Thus, the novel regulatory variation in POS1 regulates reproductive organ size in tomatillo. This work provides insight into the evolution of the genetic regulation of plant morphology.

This work has been published in Nature Communications (Wang et al., 2014, 5: 4271, doi: 10.1038/ncomms5271). This work was supported by grants from the National Natural Science Foundation of China.

 

Fig. 1 POS1 expression is positively associated with berry size variation in tomatillos.