A petunia transcription factor PhWRKY41 modulates flower senescence through reactive oxygen species detoxification

ABSTRACT Reactive oxygen species (ROS) are essential signaling molecules that induce oxidative damage to various cellular organelles in plants. However, the regulatory mechanisms underlying the ROS-mediated petal senescence are not fully understood. Here, the effects of eight up-regulated WRKY transcription factors on petal senescence of petunia were examined through virus-induced gene silencing (VIGS). Of them, down-regulation of PhWRKY41 , a putative member of subgroup IIIa, resulted in the most pronounced acceleration of flower senescence and increase in the transcription of senescence-associated marker PhSAG12. PhWRKY41 was therefore selected for further functional characterization. Through stable genetic transformation, transgenic petunia plants overexpressing PhWRKY41 exhibited a delay of 2.0–2.3 days in petal senescence compared with wild type (WT). Conversely, RNAi silencing of PhWRKY41 accelerated petal senescence by 1.5–2.1 days. Decreased and increased levels of hydrogen peroxide (H 2 O 2 ) were detected in transgenic plants with PhWRKY41 overexpression and RNAi silencing, respectively. PhWRKY41 was significantly responsive to H 2 O 2 signals, and exogenous H 2 O 2 treatment substantially mitigated flower lifespan variation among WT and transgenic petunia plants. Promoter binding assays revealed that PhWRKY41 specifically activated the transcription of alternative oxidase 3 ( PhAOX3 ), which is a repressor of ROS production. Further data verified that silencing of PhAOX3 decreased the longevity of petunia flowers with elevated H 2 O 2 content. In terms of transcriptional changes, expression trends of PhWRKY41 and PhAOX3 were opposite to that of PhSAG12 in the overexpression and silencing assays. Our findings indicate that PhWRKY41 functions as a negative modulator of flower senescence by eliminating ROS-mediated damage.