OsFH13, a type I formin, is indispensable for rice morphogenesis

Actin binding proteins regulate plant morphogenesis by regulating actin dynamics and formins affect plant morphogenesis by modulating cytoskeleton dynamics. However, the roles of formins in rice morphogenesis remain largely unclear. Here, we report the biochemical and biological functions of formin homolog 13 (OsFH13), one type I formin, in regulating rice morphogenesis. OsFH13 was found to be ubiquitously expressed in both vegetative and reproductive organs including roots, stems, leaves, and flowers; while OsFH13 was found to be localized on the plasma membrane. The osfh13 mutant displayed pleiotropic phenotypes including reduced plant height, shorter roots, shorter stems, shrank flag leaves, and smaller seeds due to defective cell elongation and expansion. In the absence of OsFH13, actin filaments arrays were found to be unstable both in vivo and in vitro. In addition, OsFH13 was also found to be able to bundle microtubules in vitro. These results demonstrate that OsFH13 is critical to rice morphogenesis via stabilizing actin network, which could be useful to breed rice with desired morphogenesis.