An abscisic acid inducible Arabidopsis MAPKKK, MAPKKK18 regulates leaf senescence via its kinase activity

Abstract

Abscisic acid (ABA) is a phytohormone that regulates many physiological functions, such as plant growth, development and stress responses. The MAPK cascade plays an important role in ABA signal transduction. Several MAPK and MAPKK molecules are reported to function in ABA signaling; however, there have been few studies related to the identification of MAPKKK upstream of MAPKK in ABA signaling. In this study, we show that an Arabidopsis MAPKKK, MAPKKK18 functions in ABA signaling. The expression of MAPKKK18 was induced by ABA treatment. Yeast two-hybrid analysis revealed that MAPKKKK18 interacted with MKK3, which interacted with C-group MAPK, MPK1/2/7. Immunoprecipitated kinase assay showed that the 3xFlag-tagged MAPKKK18, expressed in Arabidopsis plants, was activated when treated with ABA. These results indicate the possibility that the MAPK cascade is composed of MAPKKK18, MKK3 and MPK1/2/7 in ABA signaling. The transgenic plants overexpressing MAPKKK18 (35S:MAPKKK18) and its kinase negative mutant (35S:MAPKKK18 KN) were generated, and their growth was monitored. Compared with the WT plant, 35S:MAPKKK18 and 35S:MAPKKK18 KN showed smaller and bigger phenotypes, respectively. Senescence of the rosette leaves was promoted in 35S:MAPKKK18, but suppressed in 35S:MAPKKK18 KN. Furthermore, ABA-induced leaf senescence was accelerated in 35S:MAPKKK18. These results suggest that MAPKKK18 controls the plant growth by adjusting the timing of senescence via its protein kinase activity in ABA dependent manners.

AIK1, A Mitogen-Activated Protein Kinase, Modulates Abscisic Acid Responses through the MKK5-MPK6 Kinase Cascade

“…Interestingly, AIK1 overexpression seedlings gradually exhibited yellow and eventually bleached leaves (;25 d) compared to the wild-type seedlings (Supplemental Fig. S5B), and ABA-induced leaf senescence was accelerated in 35S:MAPKKK18 (Matsuoka et al, 2015). AIK1 has redundant functions with MAPKKK18 in ABA-regulated senescence.…”

“…It has been documented that several components of distinct MAPK signaling cascades involved in transcriptional regulation, protein accumulation and stability, as well as kinase activity are induced by ABA, indicating that MAPK pathways play an important role in ABA signaling in Arabidopsis (Xing et al, 2008;Jammes et al, 2009Jammes et al, , 2011Salam et al, 2013;Danquah et al, 2014Danquah et al, , 2015Han et al, 2014;López-Bucio et al, 2014;Lee et al, 2015;Matsuoka et al, 2015). However, there are few reports concerning the involvement of MAPKKK in the modulation of ABA signaling.…”

“…In plants, MAPK cascades have been shown to be involved in signaling pathways and activated by abiotic stresses such as cold, salt, touch, wounding, heat, UV, osmotic shock, and heavy metals (Tena et al, 2001;Zhang et al, 2006;Colcombet and Hirt, 2008;Liu, 2012). Recent studies have suggested that MAPK cascades are involved in several ABA responses, including antioxidant defenses, guard cell signaling, seed germination, and plant growth (Liu and Zhang, 2004;Xing et al, 2008;Jammes et al, 2009;Zong et al, 2009;Wang et al, 2010;Zhang et al, 2010;Huang et al, 2014;Danquah et al, 2015;Lee et al, 2015;Matsuoka et al, 2015). AtMKK1 and AtMPK6 were reported to link each other and mediate ABA-induced H 2 O 2 scavenger CAT1 (catalase 1) gene expression and H 2 O 2 production (Xing et al, 2008).…”

“…A phosphoproteomic approach revealed that SnRK2 promotes ABA-induced activation of the AtMPK1 and AtMPK2 (Umezawa et al, 2013). Even though it has been recently reported that MAPKKK17/ 18-MKK3-MPK1/2/7/14 is an ABA-activated MAPK cascade (Danquah et al, 2015) and that MAPKKK18 controls the plant growth by adjusting the timing of senescence via its protein kinase activity in ABAdependent matters (Matsuoka et al, 2015), the role of MAPKKKs in regulating ABA responses, such as stomatal behavior and root growth inhibition, remains largely unknown.…”

Yaprak Senesensi: Fizyolojik ve Moleküler Düzenlenmesine Bakış

“…Absisik asit (ABA) bitki büyümesi, gelişimi ve stres cevapları gibi birçok fizyolojik olayı düzenleyen bir bitki hormonudur [41]. İlk çalışmalar dışarıdan ABA uygulamasının kesik yapraklarda senesensi teşvik ettiğini göstermiştir ancak kesik olmayan yapraklarda bu etki daha azdır [8].…”