Arabidopsis thaliana homeobox 12 (ATHB12), a homeodomain‐leucine zipper protein, regulates leaf growth by promoting cell expansion and endoreduplication

Abstract

SummaryArabidopsis thaliana homeobox 12 (ATHB12), a homeodomain-leucine zipper class I (HDZip I) gene, is highly expressed in leaves and stems, and induced by abiotic stresses, but its role in development remains obscure.To understand its function during plant development, we studied the effects of loss and gain of function. Expression of ATHB12 fused to the EAR-motif repression domain (SRDX) -P 35S ::ATHB12SRDX (A12SRDX) and P ATHB12 ::ATHB12SRDX -slowed both leaf and root growth, while the growth of ATHB12-overexpressing seedlings (A12OX) was accelerated.Microscopic examination revealed changes in the size and number of leaf cells. Ploidy was reduced in A12SRDX plants, accompanied by decreased cell expansion and increased cell numbers. By contrast, cell size was increased in A12OX plants, along with increased ploidy and elevated expression of cell cycle switch 52s (CCS52s), which are positive regulators of endoreduplication, indicating that ATHB12 promotes leaf cell expansion and endoreduplication. Overexpression of ATHB12 led to decreased phosphorylation of Arabidopsis thaliana ribosomal protein S6 (AtRPS6), a regulator of cell growth. In addition, induction of ATHB12 in the presence of cycloheximide increased the expression of several genes related to cell expansion, such as EXPANSIN A10 (EXPA10) and DWARF4 (DWF4).Our findings strongly suggest that ATHB12 acts as a positive regulator of endoreduplication and cell growth during leaf development.

High Concentration of Melatonin Regulates Leaf Development by Suppressing Cell Proliferation and Endoreduplication in Arabidopsis

“…Small organ size in bin4 is primarily caused by suppressed cell expansion associated with defects in endoreduplication [80]. Overexpression of Arabidopsis thaliana homeobox 12 (ATHB12) resulted in increased cell size, along with elevated ploidy [81]. Our results showed that 1000 μM melatonin caused significantly 2C fraction increase in cotyledons, the first pair of true leaves, and the fifth leaves, in accordance with the decrease of higher DNA content (Figure 4A–C).…”

Genome-Wide Identification of MicroRNAs and Their Targets in the Leaves and Fruits of Eucommia ulmoides Using High-Throughput Sequencing

“…These miRNAs may regulate Eu-rubber accumulation via suppression of their target gene expression. Previous studies have showed that Arabidopsis thaliana homeobox 12 (ATHB12), a homeodomain-leucine zipper class I (HDZip I) gene, can regulatethe cell growth during leaf development (Hur et al, 2015). Our results indicated that the HD-ZIP expression enhanced rubber content by promoting leaf and fruit growth.…”

Dehydration‐responsive nuclear proteome landscape of chickpea (Cicer arietinum L.) reveals phosphorylation‐mediated regulation of stress response

“…Interplay between kinases and phosphatases mediates global regulation of cellular function (Li et al, ; Trotta, Konert, Rahikainen, Aro, & Kangasjärvi, ; Zhao et al, ). The reversibility of protein phosphorylation status further aids in plasticity of molecular regulation spreading its influence over replication, transcription, cell cycle progression, splicing, and epigenetic regulation (Hur et al, ; Qi et al, ; Sun et al, ; Tunc‐Ozdemir et al, ). The precise site of phosphorylation has been the study of interest in deciphering signal transduction pathways (Nühse, Stensballe, Jensen, & Peck, ).…”