Plants have developed various sophisticated mechanisms to cope up with climate extremes and different stress conditions, especially by involving specific transcription factors (TFs). The members of the WRKY TF family are well known for their role in plant development, phytohormone signaling and developing resistance against biotic or abiotic stresses. In this study, we performed a genome-wide screening to identify and analyze the WRKY TFs in pearl millet (Pennisetum glaucum; PgWRKY), which is one of the most widely grown cereal crops in the semi-arid regions. A total number of 97 putative PgWRKY proteins were identified and classified into three major Groups (I-III) based on the presence of WRKY DNA binding domain and zinc-finger motif structures. Members of Group II have been further subdivided into five subgroups (IIa-IIe) based on the phylogenetic analysis. In-silico analysis of PgWRKYs revealed the presence of various cis-regulatory elements in their promoter region like ABRE, DRE, ERE, EIRE, Dof, AUXRR, G-box, etc., suggesting their probable involvement in growth, development and stress responses of pearl millet. Chromosomal mapping evidenced uneven distribution of identified 97 PgWRKY genes across all the seven chromosomes of pearl millet. Synteny analysis of PgWRKYs established their orthologous and paralogous relationship among the WRKY gene family of Arabidopsis thaliana, Oryza sativa and Setaria italica. Gene ontology (GO) annotation functionally categorized these PgWRKYs under cellular components, molecular functions and biological processes. Further, the differential expression pattern of PgWRKYs was noticed in different tissues (leaf, stem, root) and under both drought and salt stress conditions. The expression pattern of PgWRKY33, PgWRKY62 and PgWRKY65 indicates their probable involvement in both dehydration and salinity stress responses in pearl millet. Functional characterization of identified PgWRKYs can be useful in delineating their role behind the natural stress tolerance of pearl millet against harsh environmental conditions. Further, these PgWRKYs can be employed in genome editing for millet crop improvement.

中文翻译：

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干旱和盐分胁迫下全谷粒WRKY转录因子的全基因组鉴定和表达分析

植物已经开发出各种复杂的机制来应对极端气候和不同的胁迫条件，特别是通过涉及特定的转录因子（TF）。WRKY TF家族的成员以其在植物发育，植物激素信号传导以及对生物或非生物胁迫产生抗性中的作用而闻名。在这项研究中，我们进行了全基因组筛选，以鉴定和分析珍珠粟（Pennisetum glaucum; PgWRKY）中的WRKY TF，后者是半干旱地区生长最广泛的谷物作物之一。根据WRKY DNA结合结构域和锌指基序结构的存在，共鉴定了97种假定的PgWRKY蛋白并将其分为三个主要组（I-III）。根据系统发育分析，第二组成员进一步细分为五个亚组（IIa-IIe）。对PgWRKYs进行的计算机分析表明，其启动子区域存在各种顺式调控元件，如ABRE，DRE，ERE，EIRE，Dof，AUXRR，G-box等，表明它们可能参与了生长，发育和应激反应珍珠小米。染色体作图表明在珍珠粟的所有七个染色体上已鉴定的97个PgWRKY基因分布不均。对PgWRKYs的同义分析建立了它们在拟南芥Wyty基因家族，水稻（Oryza sativa）和Setaria italica之间的直系同源和旁系同源。基因本体论（GO）注释按功能将这些PgWRKYs归类为细胞成分，分子功能和生物学过程。进一步，在不同的组织（叶，茎，根）中以及在干旱和盐胁迫条件下，都发现了PgWRKYs的差异表达模式。PgWRKY33，PgWRKY62和PgWRKY65的表达模式表明它们可能参与了珍珠粟的脱水和盐分胁迫响应。鉴定出的PgWRKYs的功能表征可用于描述其在恶劣环境条件下对珍珠小米的自然胁迫耐受性后的作用。此外，这些PgWRKY可用于基因组编辑以改善小米作物。PgWRKY62和PgWRKY65表明它们可能参与了珍珠粟的脱水和盐分胁迫响应。鉴定出的PgWRKYs的功能特性可用于描述其在珍珠小米对恶劣环境条件的自然胁迫耐受性之后的作用。此外，这些PgWRKY可用于基因组编辑以改善小米作物。PgWRKY62和PgWRKY65表明它们可能参与了珍珠粟的脱水和盐分胁迫响应。鉴定出的PgWRKYs的功能表征可用于描述其在恶劣环境条件下对珍珠小米的自然胁迫耐受性后的作用。此外，这些PgWRKY可用于基因组编辑以改善小米作物。