NIN-like protein 8 is a master regulator of nitrate-promoted seed germination in Arabidopsis

Abstract

Seeds respond to multiple different environmental stimuli that regulate germination. Nitrate stimulates germination in many plants but how it does so remains unclear. Here we show that the Arabidopsis NIN-like protein 8 (NLP8) is essential for nitrate-promoted seed germination. Seed germination in nlp8 loss-of-function mutants does not respond to nitrate. NLP8 functions even in a nitrate reductase-deficient mutant background, and the requirement for NLP8 is conserved among Arabidopsis accessions. NLP8 reduces abscisic acid levels in a nitrate-dependent manner and directly binds to the promoter of CYP707A2, encoding an abscisic acid catabolic enzyme. Genetic analysis shows that NLP8-mediated promotion of seed germination by nitrate requires CYP707A2. Finally, we show that NLP8 localizes to nuclei and unlike NLP7, does not appear to be activated by nitrate-dependent nuclear retention of NLP7, suggesting that seeds have a unique mechanism for nitrate signalling.

Changes in Gene Expression in Space and Time Orchestrate Environmentally Mediated Shaping of Root Architecture

“…We identified transcription factor modules that control modules of processes and also identified a novel root architecture role for NLP8 (Yan et al, 2016) and a new root architecture-regulating transcription factor, WRKY15, the functions of which are moderated by N abundance. The molecular regulation that we uncover underlies lateral root developmental responses under different environments, one component of root plasticity.…”

“…We analyzed T-DNA lines and found that a nlp8 homozygous loss of expression knockout mutant (nlp8-2 as named in Yan et al, 2016) has a shorter primary root and fewer lateral roots on replete levels of nitrate ( Figure 2F; Supplemental Data Set 3) but not on depleted levels of nitrate. This is consistent with findings by Yan et al (2016) who did not analyze root development but did observe N-dependent effects on germination.…”

“…NIN is a critical regulator that coordinates cell-type responses during nodulation in the legume Medicago truncatula (Vernié et al, 2015). NLP8 has recently been found to regulate N-responsive seed germination (Yan et al, 2016). We analyzed T-DNA lines and found that a nlp8 homozygous loss of expression knockout mutant (nlp8-2 as named in Yan et al, 2016) has a shorter primary root and fewer lateral roots on replete levels of nitrate ( Figure 2F; Supplemental Data Set 3) but not on depleted levels of nitrate.…”

“…To examine At2g43500 (NLP8) perturbation, a heterozygous T-DNA line in the start of the open reading frame (nlp8-2, SALK_140298) was obtained from the ABRC stock center (Scholl et al, 2000; nomenclature as in Yan et al, 2016). CS75037-4-7, harboring a T-DNA in WRKY15 (At2g23320), was isolated as part of a mutant screen of pools of T-DNA lines (CS76052) obtained from the ABRC (Scholl et al, 2000); T-DNA location (promoter) was determined using TAIL-PCR (Liu et al, 1995).…”

Seed Biology Updates – Highlights and New Discoveries in Seed Dormancy and Germination Research

“…However, the NLP8-mediated response is thought to be independent of NO signaling and a direct response to nitrate, because NO-defective mutant seeds still respond to nitrate and germinate in a NLP8-dependent manner (Yan et al, 2016). The nitrate and NO signaling pathways seem to target different transcription factors in seeds.…”