Carbohydrate partitioning is essential for plant growth and development, and its hindrance will result in excess accumulation of carbohydrates in source tissues. Most of the related mutants in maize (Zea mays L.) display impaired whole-plant sucrose transport, but other mechanisms affecting carbohydrate partitioning have seldom been reported. Here, we characterized chlorotic leaf3 (chl3), a recessive mutation causing leaf chlorosis with starch accumulation excessively in bundle sheath chloroplasts, suggesting that chl3 is de-fective in carbohydrate partitioning. Positional cloning revealed that the chl3 phenotype results from a frameshift mutation in ZmPHOH, which encodes starch phosphorylase 2. Two mutants in ZmPHOH exhibited the same phenotype as chl3, and both alleles failed to complement the chl3 mutant phenotype in an allelism test. Inactivation of ZmPHOH in chl3 leaves reduced the efficiency of transitory starch conversion, resulting in increased leaf starch contents and altered carbohydrate metabolism patterns. RNA-seq revealed the tran-scriptional downregulation of genes related to photosynthesis and carbohydrate metabolism in chl3 leaves compared to the wild type. Our results demonstrate that transitory starch remobilization is very important for cellular carbohydrate partitioning in maize, in which ZmPHOH plays an indis-pensable role.

Yao Qin;Ziyi Xiao;Hailiang Zhao;Jing Wang;Yuanru Wang;Fazhan Qiu

National Key Laboratory of Crop Genetic Improvement,Hubei Hongshan Laboratory,College of Plant Science and Technology,Huazhong Agricultural University,Wuhan 430070,China

植物学报（英文版）

[1]Yao Qin;Ziyi Xiao;Hailiang Zhao;Jing Wang;Yuanru Wang;Fazhan Qiu-.Starch phosphorylase 2 is essential for cellular carbohydrate partitioning in maize)[J].植物学报（英文版）,2022(09):1755-1769

leaf3,chl3,ZmPHOH,allelism

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