ArabidopsisCOGWHEEL1links light perception and gibberellins with seed tolerance to deterioration

Abstract

SUMMARYLight is a major regulator of plant growth and development by antagonizing gibberellins (GA), and we provide evidence for a role of light perception and GA in seed coat formation and seed tolerance to deterioration. We have identified two activation-tagging mutants of Arabidopsis thaliana, cog1-2D and cdf4-1D, with improved seed tolerance to deterioration linked to increased expression of COG1/DOF1.5 and CDF4/DOF2.3, respectively. These encode two homologous DOF transcription factors, with COG1 most highly expressed in seeds. Improved tolerance to seed deterioration was reproduced in transgenic plants overexpressing these genes, and loss of function from RNA interference resulted in opposite phenotypes. Overexpressions of COG1 and CDF4 have been described to attenuate various light responses mediated by phytochromes. Accordingly, we found that phyA and phyB mutants exhibit increased seed tolerance to deterioration. The phenotype of tolerance to deterioration conferred by gain of function of COG1 and by loss of function of phytochromes is of maternal origin, is also observed under natural aging conditions and correlates with a seed coat with increased suberin and reduced permeability. In developing siliques of the cog1-2D mutant the expression of the GA biosynthetic gene GA3OX3 and levels of GA 1 are higher than in the wild type. These results explain the antagonism between phytochromes and COG1 in terms of the inhibition and the activation, respectively, of GA action.

PRX2 and PRX25, peroxidases regulated by COG1, are involved in seed longevity in Arabidopsis

“…COG1 (At1g29160) is a TF that positively regulates the tolerance of Arabidopsis seeds to deterioration. The most likely mechanism of the gain of function mutant cog1‐2D is the high accumulation of suberin in the PL layer of the seed coat (Bueso et al, ). To confirm this hypothesis, we carried out a deterioration test of full germination capacity of seeds from mutants affected in suberin content.…”

“…During the last years, we have been trying to define the molecular mechanism underpinning COG1 and ATHB25‐mediated resistance to seed aging. Overexpression of these TFs produces seeds with an increase in the accumulation of suberin in the PL layer of the seed coat, likely reducing the embryo oxidation and extending seed viability (Bueso et al, ; Bueso et al, ). The specific target genes and processes involved in mediating this reinforcement of the seed coat is the next issue to clarify.…”

“…On the other hand, overexpression of COG1 increases gibberellin levels during seed maturation (Bueso et al, 2016) and some peroxidases are induced by exogenous application of GA3 (Wang, Que, Xu, Wang, & Xiong, 2017;Zieslin & Ben-Zaken, 1992). To ascertain whether COG1-regulated seed coat peroxidases are induced by this growth hormone, siliques from GA3-treated plants were collected and peroxidase gene expression was analysed.…”

“…I. Molina (Beisson et al, 2007) and Dr. JW Reed (Yadav et al, 2014), respectively. The cog1-2D is an activation mutant isolated in our laboratory (Bueso et al, 2016)…”

The DOF Transcription Factors in Seed and Seedling Development

“…COG1 is also involved in seed tolerance to deterioration, the process of loss of vigour and viability: indeed, the dominant allele cog1-2D that overexpresses COG1 displayed increased tolerance to deterioration, a phenotype dependent on a higher GA level and a reduced permeability of the seed coat [89]. This phenotype is in agreement with the negative role of COG1 in light signalling, since Red and Far Red light have a negative role in seed tolerance to deterioration, as indicated by the increased tolerance of the phyB-9 and phyA-211 mutant seeds [89]. In addition, it has recently been demonstrated that COG1 controls the expression of the peroxidases PRX2 and PRX25, which are involved in the polymerisation of suberin in the seed coat [90].…”