MicroRNAs (miRNAs) are～21-nucleotide noncoding RNAs that play critical roles in regulating plant growth and development through directing the degradation of target mRNAs. Axillary meristem activity, and hence shoot branch-ing, is influenced by a complicated network that involves phytohormones such as auxin, cytokinin, and strigolactone. GAI, RGA, and SCR (GRAS) family members take part in a variety of developmental processes, including axillary bud growth. Here, we show that theArabidopsis thaliana microRNA171c (miR171c) acts to negatively regulate shoot branching through targeting GRAS gene family members SCARECROW-LIKE6-11 (SCL6-11), SCL6-111, and SCL6-1Vfor cleavage. Transgenic plants overexpressing MIR171c (35Spro-MIR171c) and sol6-11 scl6-111 scl6-1V triple mutant plants exhibit a similar reduced shoot branching phenotype. Expression of any one of the miR171c-resistant versions of SCL6-11, SCL6-111, and SCL6-1V in 35Spro-MIR171c plants rescues the reduced shoot branching phenotype. Scl6-11 scl6-111 scl6-1V mutant plants exhibit pleiotropic phenotypes such as increased chlorophyll accumulation, decreased primary root elongation, and abnormal leaf and flower patterning. SCL6-Ⅱ, SCL6-Ⅲ, and SCI.6-Ⅳ are located to the nucleus, and show transcriptional activation activity. Our results suggest that miR171c-targeted SCL6-Ⅱ, SCL6-Ⅲ, and SCL6-Ⅳ play an important role in the regulation of shoot branch production.
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