Cytokinin group of phytohormones regulate root elongation and branching during post‐embryonic development. Cytokinin‐degrading enzymes cytokinin oxidases/dehydrogenases (CKXs) have been deployed to investigate biological activities of cytokinin and to engineer root growth. We expressed chickpea cytokinin oxidase 6 (CaCKX6) under the control of a chickpea root‐specific promoter of CaWRKY31 in Arabidopsis thaliana and chickpea having determinate and indeterminate growth patterns, respectively, to study the effect of cytokinin depletion on root growth and drought tolerance. Root‐specific expression of CaCKX6 led to a significant increase in lateral root number and root biomass in Arabidopsis and chickpea without any penalty to vegetative and reproductive growth of shoot. Transgenic chickpea lines showed increased CKX activity in root. Soil‐grown advanced chickpea transgenic lines exhibited higher root‐to‐shoot biomass ratio and enhanced long‐term drought tolerance. These chickpea lines were not compromised in root nodulation and nitrogen fixation. The seed yield in some lines was up to 25% higher with no penalty in protein content. Transgenic chickpea seeds possessed higher levels of zinc, iron, potassium and copper. Our results demonstrated the potential of cytokinin level manipulation in increasing lateral root number and root biomass for agronomic trait improvement in an edible legume crop with indeterminate growth habit.

中文翻译：

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鹰嘴豆细胞分裂素氧化酶/脱氢酶6的根特异性表达可提高根的生长，耐旱性和产量，而不会影响结瘤。

植物激素的细胞分裂素组在胚后发育过程中调节根的伸长和分支。细胞分裂素降解酶细胞分裂素氧化酶/脱氢酶（CKXs）已被用于研究细胞分裂素的生物学活性和工程根生长。我们在拟南芥和鹰嘴豆具有确定的和不确定的生长模式的鹰嘴豆根特异性启动子CaWRKY31的控制下表达了鹰嘴豆细胞分裂素氧化酶6（CaCKX6），以研究细胞分裂素消耗对根生长和耐旱性的影响。CaCKX6的根特异性表达导致拟南芥侧根数和根生物量显着增加和鹰嘴豆，不会对芽的营养和生殖生长造成任何损害。转基因鹰嘴豆品系显示根部的CKX活性增加。土壤生长的高级鹰嘴豆转基因品系具有更高的根茎比生物量比和增强的长期干旱耐受性。这些鹰嘴豆品系在根瘤和固氮方面没有受到损害。一些品系的种子产量提高了25％，而蛋白质含量没有损失。转基因鹰嘴豆种子具有较高水平的锌，铁，钾和铜。我们的结果证明了细胞分裂素水平操纵在增加侧根数和根生物量方面的潜力，可改善具有不确定生长习性的可食用豆类作物的农艺性状。