Abstract
Leaf senescence is a programmed developmental process regulated by various endogenous and exogenous factors. Here we report the characterization of the senescence-regulating role of DEAR4 (AT4G36900) from the DREB1/CBF (dehydration-responsive element binding protein 1/C-repeat binding factor) family in Arabidopsis. The expression of DEAR4 is associated with leaf senescence and can be induced by ABA, JA, darkness, drought and salt stress. Transgenic plants over-expressing DEAR4 showed a dramatically enhanced leaf senescence phenotype under normal and dark conditions while the dear4 knock-down mutant displayed delayed senescence. DEAR4 over-expressing plants showed decreased seed germination rate under ABA and salt stress conditions as well as decreased drought tolerance, indicating that DEAR4 was involved in both senescence and stress response processes. Furthermore, we found that DEAR4 protein displayed transcriptional repressor activities in yeast cells. DEAR4 could directly repress the expression of a subset of COLD-REGULATED (COR) and RESPONSIVE TO DEHYDRATION (RD) genes which have been shown to be involved in leaf longevity and stress response. Also we found that DERA4 could induce the production of Reactive oxygen species (ROS), the common signal of senescence and stress responses, which gives us the clue that DEAR4 may play an integrative role in senescence and stress response via regulating ROS production.
Highlights
Senescence is the last stage of leaf development which is influenced by intrinsic and environmental factors including age, nutrients, hormones, darkness, osmotic stress, extreme temperature and pathogens (Lim et al, 2007; Guo and Gan, 2014)
To identify new genes regulated by both senescence and light, the GENEVESTIGATOR database1 was screened and DEAR4 was found to be highly expressed in senescing plant tissues, induced by dark conditions
As one of the AP2/ERF subfamilies, members of the DREB protein family have been extensively studied over the years due to their crucial roles in regulation of abiotic- and biotic-stress responses
Summary
Senescence is the last stage of leaf development which is influenced by intrinsic and environmental factors including age, nutrients, hormones, darkness, osmotic stress, extreme temperature and pathogens (Lim et al, 2007; Guo and Gan, 2014). During the process of leaf senescence, cellular. Degradation of macromolecules in senescing leaves functions to remobilize nutrients to support young vegetative organs and reproductive growth. A number of SAGs have been identified to play a regulatory role in leaf senescence. These include genes encoding transcription factors of WRKY, NAC, DREB, MYB, and bZIP family (Woo et al, 2001; Yang et al, 2011; Lee et al, 2012; Vainonen et al, 2012)
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