Table_3_Morphophysiological and transcriptome analysis reveal that reprogramming of metabolism, phytohormones and root development pathways governs the potassium (K+) deficiency response in two contrasting chickpea cultivars.xlsx

Potassium (K+) is an essential macronutrient for plant growth and development. K+ deficiency hampers important plant processes, such as enzyme activation, protein synthesis, photosynthesis and stomata movement. Molecular mechanism of K+ deficiency tolerance has been partly understood in model plants Arabidopsis, but its knowledge in legume crop chickpea is missing. Here, morphophysiological analysis revealed that among five high yielding desi chickpea cultivars, PUSA362 shows stunted plant growth, reduced primary root growth and low K+ content under K+ deficiency. In contrast, PUSA372 had negligible effect on these parameters suggesting that PUSA362 is K+ deficiency sensitive and PUSA372 is a K+ deficiency tolerant chickpea cultivar. RNA-seq based transcriptome analysis under K+ deficiency revealed a total of 820 differential expressed genes (DEG’s) in PUSA362 and 682 DEGs in PUSA372. These DEGs belongs to different functional categories, such as plant metabolism, signal transduction components, transcription factors, ion/nutrient transporters, phytohormone biosynthesis and signalling, and root growth and development. RNA-seq expression of randomly selected 16 DEGs was validated by RT-qPCR. Out of 16 genes, 13 showed expression pattern similar to RNA-seq expression, that verified the RNA-seq expression data. Total 258 and 159 genes were exclusively up-regulated, and 386 and 347 genes were down-regulated, respectively in PUSA362 and PUSA372. 14 DEGs showed contrasting expression pattern as they were up-regulated in PUSA362 and down-regulated in PUSA372. These include somatic embryogenesis receptor-like kinase 1, thaumatin-like protein, ferric reduction oxidase 2 and transcription factor bHLH93. Nine genes which were down-regulated in PUSA362 found to be up-regulated in PUSA372, including glutathione S-transferase like, putative calmodulin-like 19, high affinity nitrate transporter 2.4 and ERF17-like protein. Some important carbohydrate metabolism related genes, like fructose-1,6-bisphosphatase and sucrose synthase, and root growth related Expansin gene were exclusively down-regulated, while an ethylene biosynthesis gene 1-aminocyclopropane-1-carboxylate oxidase 1 (ACO1) was up-regulated in PUSA362. Interplay of these and several other genes related to hormones (auxin, cytokinin, GA etc.), signal transduction components (like CBLs and CIPKs), ion transporters and transcription factors might underlie the contrasting response of two chickpea cultivars to K+ deficiency. In future, some of these key genes will be utilized in genetic engineering and breeding programs for developing chickpea cultivars with improved K+ use efficiency (KUE) and K+ deficiency tolerance traits.

钾离子（K+）是植物生长与发育所必需的重要大量营养素。钾离子缺乏会阻碍植物众多关键过程，例如酶的活化、蛋白质合成、光合作用以及气孔运动。在模式植物拟南芥中，钾离子缺乏耐受的分子机制已被部分解析，然而在豆科作物鹰嘴豆中的相关知识尚属空白。本研究通过形态生理学分析发现，在五种高产鹰嘴豆品种中，PUSA362在钾离子缺乏条件下表现出植株生长受阻、主根生长减少以及钾离子含量低的现象。相较之下，PUSA372对上述参数的影响微乎其微，这表明PUSA362对钾离子缺乏敏感，而PUSA372则是一种耐受钾离子缺乏的鹰嘴豆品种。基于RNA测序的转录组分析揭示了PUSA362在钾离子缺乏条件下共有820个差异表达基因（DEG），而在PUSA372中则有682个DEG。这些DEG分属于不同的功能类别，例如植物代谢、信号转导组分、转录因子、离子/营养素转运蛋白、植物激素的生物合成与信号传导，以及根的生长与发育。对随机选取的16个DEG进行RNA测序表达验证，其中13个基因的表达模式与RNA测序结果相似，从而验证了RNA测序数据的可靠性。在PUSA362中，共有258个基因特异性上调，386个基因特异性下调；而在PUSA372中，则有159个基因特异性上调，347个基因特异性下调。14个DEG表现出相反的表达模式，它们在PUSA362中上调而在PUSA372中下调，包括体细胞胚胎发生受体样激酶1、亲硫蛋白、铁还原氧化酶2和转录因子bHLH93。在PUSA362中下调的9个基因在PUSA372中上调，包括谷胱甘肽转移酶样蛋白、推测的钙调蛋白样19、高亲和力硝酸盐转运蛋白2.4和ERF17样蛋白。一些与碳水化合物代谢密切相关的重要基因，如果糖-1,6-二磷酸酶和蔗糖合酶，以及与根生长相关的 expansin 基因均特异性下调，而乙烯生物合成基因1-氨基环丙烷-1-羧酸氧化酶1（ACO1）在PUSA362中上调。这些基因及其与激素（如生长素、细胞分裂素、GA等）、信号转导组分（如CBLs和CIPKs）、离子转运蛋白和转录因子的相互作用可能构成了两种鹰嘴豆品种对钾离子缺乏反应差异的基础。在未来，这些关键基因将被应用于遗传工程和育种计划中，以培育具有改进的钾离子利用效率（KUE）和钾离子缺乏耐受特性的鹰嘴豆品种。