Repression of microRNA 160 results in retarded seed integument growth and smaller final seed size in cotton

microRNA 160(miR160),targeting auxin response factors(ARFs),plays many roles in plant development.We investigated the role of the mi R160/ARF axis in regulation of cotton seed size.Suppressing mi R160 activity,specifically in the seed coat,led to smaller seeds and less fiber production owing to attenuated growth of the maternal integument.Scanning electron microscopy and histology showed that expansion of cells in the integument was retarded in mi R160-suppressed lines.Four Gh ARF genes were targeted by mi R160 and were upregulated in mi R160-suppressed lines,indicating that a mi R160/ARF axis is present in cotton.Five genes(Ghir_A05 G003740,Scaffold1878 G000010,Ghir_D09 G024980,Ghir_A11 G010730,and Ghir_A05 G041590),associated with reduced seed development were downregulated in mi R160-suppressed lines.Our results suggest that the mi R160/ARF axis controls maternal integument growth to influence seed size by directly or indirectly regulating seed development-associated genes.