CHOTTO1, a Double AP2 Domain Protein of Arabidopsis thaliana, Regulates Germination and Seedling Growth Under Excess Supply of Glucose and Nitrate

Abstract

Arabidopsis chotto1 (cho1) mutants show resistance to (-)-R-ABA, an ABA analog, during germination and seedling growth. Here, we report cloning and characterization of the CHO1 gene. cho1 mutants showed only subtle resistance to (+)-S-ABA during germination. The cho1 mutation acts as a strong enhancer of the abi5 mutant, whereas the cho1 abi4 double mutant showed ABA resistance similar to the abi4 single mutant. This suggests that CHO1 and ABI4, but not ABI5, act in the same genetic pathway. Map-based cloning revealed that the CHO1 gene encodes a putative transcription factor containing double AP2 domains. The CHO1 gene was expressed predominantly in seed, with the strongest expression in imbibed seed. Induction of CHO1 expression was observed 4 h after seed imbibition and reached a maximum level at 24 h. Induction of CHO1 expression did not occur in the abi4 mutants, indicating that this is an ABI4-dependent process. Microarray experiments showed that a large number of genes involved in primary metabolism and the stress response were up-regulated in the cho1 mutant. Growth of abi4 and cho1 mutant seedlings was resistant to high concentrations of glucose. In addition, growth of cho1 mutant seedlings was partially resistant to excess nitrate (50 mM), as evident from their expanded green cotyledons. However, their growth was normal under moderate nitrate concentrations (< 10 mM). This nitrate response was specific to the cho1 mutants and was not observed in the abi4 mutants. Taken together, our results indicate that CHO1 regulates nutritional responses downstream of ABI4 during germination and seedling growth.

ZRF1 Chromatin Regulators Have Polycomb Silencing and Independent Roles in Development

“…Consistently, the atzrf1a atzrf1b and atbmi1a atbmi1b mutants show derepression of ABI3, CRU1/CRA1, CRU3, CHO1/AIL5, and PER1. These seed developmental genes have been demonstrated to negatively regulate seed germination (Parcy et al, 1994;Haslekås et al, 2003;Yamagishi et al, 2009). The AtBMI1b and AtRING1a proteins interact physically with the plant-specific PHD domain proteins of the ALFIN1-like (AL) family (Molitor et al, 2014).…”

Environmental nitrate signals through abscisic acid in the root tip

“…Excess nitrate signals through both the CHOTTO1 transcription factor as well as ABI4, indicating a central role for ABA. 59,60 Does this response also involve repression of SCR? What happens to ABA accumulation following a stressful treatment of excess nitrate?…”

The SWI2/SNF2 Chromatin Remodeling ATPase BRAHMA Represses Abscisic Acid Responses in the Absence of the Stress Stimulus inArabidopsis

“…To elucidate the placement of BRM in this genetic pathway, we generated a double mutant between brm-3 and the abi5-7 null mutant (Yamagishi et al, 2009). The brm-3 allele was employed so we could assay the response in homozygous germinated embryos.…”