MADS-box factor AGL16 negatively regulates drought resistance via stomatal density and stomatal movement

Abstract

Drought is one of the most severe environmental factors limiting plant growth and productivity. Plants respond to drought by closing stomata to reduce water loss.The molecular mechanisms underlying plant drought resistance are very complex and yet to be fully understood. While much research attention has been focused on the positive regulation of stomatal closure, less is known about its negative regulation, equally important in this reversible process. Here we show that the MADS-box transcriptional factor AGL16 acts as a negative regulator in drought resistance by regulating both stomatal density and movement. Loss-of-function mutant agl16 was more resistant to drought stress with higher relative water content, which was attributed to a reduced leaf stomatal density and more sensitive stomatal closure due to a higher leaf ABA level compared with wild type, while AGL16 overexpression lines displayed the opposite phenotypes. AGL16 is preferentially expressed in guard cells and down regulated in response to drought stress. The expression of CYP707A3 and AAO3 in ABA metabolism and SDD1 in stomatal development was altered by AGL16 as shown in agl16 and overexpression lines. Chromatin immunoprecipitation, transient transactivation, and yeast-one-hybrid assays demonstrated that AGL16 bound the CArG motif in the promoter of the CYP707A3, AAO3, and SDD1 to regulate their transcription, and therefore alter leaf stomatal density and ABA level.Taken together, AGL16 acts as a negative regulator of drought resistance by modulating leaf stomatal density and ABA accumulation.

AGL16 regulates genome-wide gene expression and flowering time with partial dependency on SOC1 in Arabidopsis

“…Taken together, these data suggest a regulatory role of AGL16 in water adaptation and seed germination. Corroborating with this, AGL16 was recently identified as a negative factor of drought resistance via regulation on stomata density and ABA accumulation (Zhao et al 2020). CYP707A3 (Zhao et al 2020), CYP707A1 and AAO2 , which are involved in ABA biosynthesis and metabolism, were among the AGL16 targets (Table S3).…”

“…Corroborating with this, AGL16 was recently identified as a negative factor of drought resistance via regulation on stomata density and ABA accumulation (Zhao et al 2020). CYP707A3 (Zhao et al 2020), CYP707A1 and AAO2 , which are involved in ABA biosynthesis and metabolism, were among the AGL16 targets (Table S3). Since ABA related signaling genes were also enriched in AGL16-SOC1 common targets (Fig.…”

“…9A), suggesting that miR824 -regulated AGL16 could regulate the response to water deficiency. The change in water loss could be either caused by the reduction of stomata density (Kutter et al 2007) and/or by altering the stomata aperture size, which is tightly associated with the ABA signaling pathway (Zhao et al 2020).…”

Beyond What Your Retina Can See: Similarities of Retinoblastoma Function between Plants and Animals, from Developmental Processes to Epigenetic Regulation

“…Moreover, in both organisms, members of the MADS-box family participate in these processes: MEF2 is involved in early stages of muscle differentiation and in cell proliferation of other tissues ( Figure 3 B) [ 221 , 222 , 223 ]. Similarly, a plant MADS-box gene, AGAMOUS-LIKE16 ( AGL16 ), is expressed and participates in GC development ( Figure 3 D) [ 224 , 225 ]. AGL16 mediates the stomata development process at the MMC cell lineage level and represses FAMA as well as other genes involved in the development and differentiation of guard cells ( Figure 3 C) [ 225 , 226 ].…”

“…Similarly, a plant MADS-box gene, AGAMOUS-LIKE16 ( AGL16 ), is expressed and participates in GC development ( Figure 3 D) [ 224 , 225 ]. AGL16 mediates the stomata development process at the MMC cell lineage level and represses FAMA as well as other genes involved in the development and differentiation of guard cells ( Figure 3 C) [ 225 , 226 ].…”