Ethylene response factor (ERF) genes have been characterized in numerous plants in which they are involved in responses to biotic and abiotic stress, including cold and heat stress. Cool temperatures is one of the most effective storage methods for delaying browning of fresh-cut lotus (Nelumbo nucifera) root. In model plants, ERF genes have been identified as being responsive to cold and heat stress. Whether ERF is associated with lotus root browning in cooler temperatures has not been studied. In this research, low-temperature storage (4 °C) effectively delayed browning of fresh-cut lotus root. Using RNA sequencing, seven Nelumbo nucifera ERF (NnERF) genes were isolated and studied. Transcriptional analysis indicated NnERF genes responded differently to temperature. NnERF3/4/5 were reduced continuously by a low temperature (4 °C) and NnERF5 was the most strongly downregulated. In contrast, transcripts of NnERF1/2/7 were increased at a low temperature (4 °C). The expression of NnERF6 showed no obvious difference between the two different temperatures. It is proposed that NnERF3/4/5 could be important candidates as regulators of fresh-cut lotus root browning. The roles of other members are also discussed.
Ting Min, Jun Xie, Yang Yi, Wenfu Hou, Youwei Ai and Hongxun Wang
Ting Min, En-chao Liu, Jun Xie, Yang Yi, Li-mei Wang, You-wei Ai and Hong-xun Wang
Ethylene response factor (ERF) genes have been involved in responses to biotic and abiotic stress, including hypoxia and anaerobic stress. Vacuum packaging (a typical anaerobic stress) is an effective storage method used to delay browning of fresh-cut lotus root (Nelumbo nucifera). In model plants, ERF genes have been identified as responsive to hypoxia. Whether ERF is associated with browning of vacuum-packaged lotus root has not been studied. The effects of vacuum packaging on browning, phenolic content, the enzyme activity of phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD), and PPO, PAL, POD, and ERF genes expression in fresh-cut lotus root were studied. Downregulation of NnPAL1, NnPPOA, and NnPOD2/3 attributable to vacuum packaging coincided with increased related enzyme activities and the degree of browning of fresh-cut lotus root. The expression patterns of NnERF4/5 were consistent with the changes in NnPAL1, NnPPOA, and NnPOD2/3 gene expression. It has been proposed that NnERF4/5 could have be important regulators of fresh-cut lotus root browning, and that the relationships of NnERF4/5 and NnPAL1, NnPPOA, and NnPOD2/3 should to be studied further.
Ting Min, Li-Fang Niu, Jun Xie, Yang Yi, Li-mei Wang, You-wei Ai and Hong-xun Wang
NAC transcription factors have been characterized in numerous plants, and the NAC gene has been shown to be involved not only in plant growth and development, but also in plant responses to abiotic and biological stresses, such as drought, high salinity, low temperature, and anaerobic/hypoxic stress. Creating an environment of anaerobic/hypoxic stress has been shown to be one of the effective storage methods for delaying the browning of fresh-cut lotus (Nelumbo nucifera) root. However, whether NAC is associated with lotus root browning under anaerobic stress has not been studied. In this study, vacuum packaging (VP; anaerobic/hypoxic stress) effectively delayed the browning of fresh-cut lotus root. The changes in the expressions of NnPAL1, NnPPOA, and NnPOD2/3 were consistent with phenylalanine aminolase, polyphenol oxidase (PPO), and peroxidase (POD) enzyme activity changes and lotus root browning. Using RNA sequencing, five NnNAC genes were isolated and studied. Transcriptional analysis indicates that the NnNAC genes showed different responses to VP. The expressions of NnNAC1/4 were inhibited by VP, which was consistent with the observed change in the degree of fresh-cut lotus root browning. However, NnNAC2 messenger RNA (mRNA) levels were upregulated, and the expressions of NnNAC3/5 showed no clear differences under different packaging scenarios. Thus, NnNAC1/4 were identified as promising candidates for further transcriptional regulation analysis in lotus root to understand more fully the molecular mechanism of browning under anaerobic/anoxic stress.
Cui-ping Hua, Zhong-kui Xie, Zhi-jiang Wu, Yu-bao Zhang, Zhi-hong Guo, Yang Qiu, Le Wang and Ya-jun Wang
The autotoxicity of root exudates and the change of rhizosphere soil microbes are two important factors that affect the quality and yield of Lanzhou lily (Lilium davidii var. unicolor). Phthalic acid (PA) is a major autotoxin of the root exudates in Lanzhou lily. In this study, we treated plants with different concentrations of PA from the Lanzhou lily root exudates and then analyzed the effects of autotoxins on fresh weight, shoot height, root length, and Oxygen Radical Absorbance Capacity in root. The diversity of soil fungi in Lanzhou lily soil was analyzed using MiSeq. The results showed that PA induced oxidative stress and oxidative damage of Lanzhou lily roots, improved the level of the membrane lipid peroxidation, reduced the content of antioxidant defense enzyme activity and the nonenzymatic antioxidant, and eventually inhibited the growth of the Lanzhou lily. We found that continuous cropping of Lanzhou lily resulted in an increase in fungal pathogens, such as Fusarium oxysporum in the soil, and reduced the size of plant-beneficial bacteria populations. The results in this study indicate that continuous cropping would damage the regular growth of Lanzhou lily.