水稻黄化早抽穗突变体 hz1 的基因鉴定及功能分析.

[Objective] The heading date of rice（Oryza sativa）is an important agronomic trait and crucial for the regional adaptability and yields. Identification and functional analysis of heading date-associated genes may provide important gene resources for the breeding in rice. [Method] BSA-seq was performed to identify target gene of a yellowish and early heading mutant huangzao 1（hz1）. RT-qPCR was used to analyze the expression profile of target genes. The subcellular localization of HZ1 was determined by transient transformation between rice protoplasts and tobacco cells. Meanwhile, the heading dates, chlorophyll content and hydrogen peroxide content were measured to analyze the phenotype of hz1 mutant. [Result] Field phenotypic observations found that hz1 showed early heading phenotype. The heading date of hz1 mutant was the same under long-day（LD）and short-day（SD）conditions, which were 43 d and 26 d earlier than those of wild type（WT）respectively, indicating that hz1 was a photoperiod-insensitive mutant. Moreover, hz1 demonstrated a yellowish phenotype, with a decrease in chlorophyll content compared with WT. Genetic analysis revealed that hz1 was controlled by a recessive gene. BSA-seq（Bulk segregation analysis with whole-genome sequencing）of F2 pools indicated that the causal gene was linked with molecular markers on the chromosome 6 with 17.8 Mb region. Further analysis demonstrated that LOC_Os06g40080 site with a T-DNA insertion was completely linkage with hz1 mutant. LOC_Os06g40080 site was an identified SE5 gene encoding heme oxygenase 1（HO1）. Expression pattern analysis revealed that HZ1/SE5 was highly expressed in the leaves and dhad diurnal rhythm expression. Subcellular localization assay showed that HZ1/SE5 protein was localized in chloroplasts. Gene expression analysis showed that HZ1/SE5 regulated the expression of florigen genes Hd3a and RFT1 to modulate the heading date in rice. In addition, HZ1/SE5 can also regulate the expression of genes associated with chlorophyll synthesis pathway to modulate the change of chlorophyll levels. [Conclusion] hz1 mutant is a photoperiodic insensitive mutant due to the mutation of heme oxygenase gene SE5. HZ1/SE5 may regulate the expression of the florigen genes and chlorophyll synthesis-associated genes to influence the heading date and leaf yellowish in rice. [ABSTRACT FROM AUTHOR]