The SIAMESE (SIM) locus is a cell-cycle kinase inhibitor (CKI) gene that has to date been identified only in plants; it encodes a protein that promotes transformation from mitosis to endoreplication. Members of the SIAMESE-RELATED (SMR) family have similar functions, and some are related to cell-cycle responses and abiotic stresses. However, the functions of SMRs are poorly understood in maize (Zea mays L.). In the present study, 12 putative SMRs were identified throughout the entire genome of maize, and these were clustered into six groups together with the SMRs from seven other plant species. Members of the ZmSMR family were divided into four groups according to their protein sequences. Various cis-acting elements in the upstream sequences of ZmSMRs responded to abiotic stresses. Expression analyses revealed that all ZmSMRs were upregulated at 5, 20, 25, and 35 days after pollination. In addition, we found that ZmSMR9/11/12 may have regulated the initiation of endoreplication in endosperm central cells. Additionally, ZmSMR2/10 may have been primarily responsible for the endoreplication regulation of outer endosperm or aleurone cells. The relatively high expression levels of almost all ZmSMRs in the ears and tassels also implied that these genes may function in seed development. The effects of treatments with ABA, heat, cold, salt, and drought on maize seedlings and expression of ZmSMR genes suggested that ZmSMRs were strongly associated with response to abiotic stresses. The present study is the first to conduct a genome-wide analysis of members of the ZmSMR family by investigating their locations in chromosomes, identifying regulatory elements in their promoter regions, and examining motifs in their protein sequences. Expression analysis of different endosperm developmental periods, tissues, abiotic stresses, and hormonal treatments suggests that ZmSMR genes may function in endoreplication and regulate the development of reproductive organs. These results may provide valuable information for future studies of the functions of the SMR family in maize.

中文翻译：

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玉米中与SIAMESE相关的家族基因的全基因组进化特征和表达分析。

SIAMESE（SIM）基因座是一种细胞周期激酶抑制剂（CKI）基因，迄今为止仅在植物中被鉴定；它编码一种蛋白质，促进从有丝分裂到内复制的转化。与SIAMESE有关（SMR）家族的成员具有相似的功能，其中一些与细胞周期反应和非生物胁迫有关。但是，在玉米（Zea mays L.）中对SMR的功能了解甚少。在本研究中，在玉米的整个基因组中鉴定出12个推定的SMR，并将它们与其他7种植物的SMR一起分为6个组。ZmSMR家族的成员根据其蛋白质序列分为四类。ZmSMRs上游序列中的各种顺式作用元件响应非生物胁迫。表达分析表明，所有ZmSMR在5时均上调。授粉后20、25和35天。此外，我们发现ZmSMR9 / 11/12可能已经调节了胚乳中央细胞内复制的起始。另外，ZmSMR2 / 10可能主要负责外部胚乳或糊粉细胞的内复制调节。几乎所有ZmSMR在耳朵和流苏中的相对较高的表达水平也暗示这些基因可能在种子发育中起作用。ABA，热，冷，盐和干旱处理对玉米幼苗和ZmSMR基因表达的影响表明ZmSMR与非生物胁迫的响应密切相关。本研究是第一个通过调查ZmSMR家族成员在染色体中的位置，鉴定其启动子区域中的调控元件，对ZmSMR家族成员进行全基因组分析的方法，并检查其蛋白质序列中的基序。对不同胚乳发育时期，组织，非生物胁迫和激素治疗的表达分析表明，ZmSMR基因可能在内复制中起作用，并调节生殖器官的发育。这些结果可能为今后SMR家族在玉米中的功能研究提供有价值的信息。