Mitogen-activated protein kinase cascades play pivotal roles in mediating environmental stress responses and plant development. In this study, a loss-of-function mutant of Arabidopsis, map3kθ1, exhibited wider stomatal openings, reduced root elongation, and increased seed germination rate compared with its wild type under exogenous abscisic acid (ABA) treatment. MAP3Kθ1 encodes a MAP kinase kinase kinase (MAP3K) with unknown function. Two overexpression lines of MAP3Kθ1 exhibited inhibited seed germination and narrowed stomata, which were aggravated by ABA treatment. Upregulation of MAP3Kθ1 also resulted in stronger drought tolerance, whereas map3kθ1 was more sensitive to water deficiency, partially due to differences in the water-holding capacity of leaves. The MAP3Kθ1-overexpressing lines also showed a greater ability to maintain root elongation under exogenous ABA. Expression of MAP3Kθ1 was inhibited by ABA, H₂O₂, and methyl viologen treatments in roots. The MAP3Kθ1-overexpressing lines accumulated more ABA by promoting its biogenesis and inhibiting its catabolism, whereas the map3kθ1 mutant accumulated less ABA, compared with wild-type plants. These findings indicate that MAP3Kθ1 promotes ABA accumulation to regulate stomatal movement, root elongation, and seed germination, while the ABA–H₂O₂ signaling module inhibits MAP3Kθ1 expression through feedback regulation.

中文翻译：

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MAP3Kθ1参与脱落酸信号在拟南芥中的耐旱性和种子萌发

Mitogen-activated protein kinase cascades play pivotal roles in mediating environmental stress responses and plant development. In this study, a loss-of-function mutant of Arabidopsis, map3kθ1, exhibited wider stomatal openings, reduced root elongation, and increased seed germination rate compared with its wild type under exogenous abscisic acid (ABA) treatment. MAP3Kθ1 encodes a MAP kinase kinase kinase (MAP3K) with unknown function. Two overexpression lines of MAP3Kθ1 exhibited inhibited seed germination and narrowed stomata, which were aggravated by ABA treatment. Upregulation of MAP3Kθ1 also resulted in stronger drought tolerance, whereas map3kθ1 was more sensitive to water deficiency, partially due to differences in the water-holding capacity of leaves. The MAP3Kθ1-overexpressing lines also showed a greater ability to maintain root elongation under exogenous ABA. Expression of MAP3Kθ1 was inhibited by ABA, H₂O₂, and methyl viologen treatments in roots. The MAP3Kθ1-overexpressing lines accumulated more ABA by promoting its biogenesis and inhibiting its catabolism, whereas the map3kθ1 mutant accumulated less ABA, compared with wild-type plants. These findings indicate that MAP3Kθ1 promotes ABA accumulation to regulate stomatal movement, root elongation, and seed germination, while the ABA–H₂ O ₂信号模块通过反馈调节抑制MAP3Kθ1表达。