基于液泡膜质子泵的硝态氮再利用研究进展

Nitrate nitrogen reutilization based on proton pump of vacuole membrane: A review

液泡大量贮存的NO3--N不能及时转入细胞质还原再利用,是造成植物大量累积NO3--N和阻碍氮素利用效率进一步提高的主要原因。本文阐述了液泡膜上NO3--N的转运机制,在液泡膜上存在着两种功能和物理特性完全不同的质子泵,即H+-ATPase和H+-PPase,这两个质子泵分别以Mg·ATP和Mg·PPi为底物,水解得到的H+被泵进液泡中,从而造成细胞质与液泡之间的H+电化学梯度,而后者在很大程度上决定着硝酸盐从液泡中外流至细胞质中的过程,硝酸盐从细胞质进入液泡主要靠液泡膜上的H+/NO3-反运门(antiport)来完成,而液泡膜上硝酸盐与其他阴离子构成的共运门(symport)则有利于液泡中的硝酸盐向细胞质转移。液泡膜质子泵对NO3--N的转运还受到细胞质硝酸还原酶(NR)活性的影响,细胞质NR可以不断同化还原NO3--N,从而使储存于液泡的NO3--N更多地转运到细胞质加以利用。这些都将为进一步研究有效、可行的氮素利用措施,提高NO3--N再利用效率提供参考。

The fact that large amount of NO3- -N accumulated in vacuole cannot be timely transported into cytoplasm and then reduced and reutilized is the main reason for the great NO3- -N accumulation in vacuole and for the nitrogen use efficiency unable to be further improved. This paper reviewed the transportation mechanisms of NO3- -N in vacuole membrane. Vacuole membrane has two proton pumps, H＋-ATPase and H＋-PPase, which have absolutely different biological functions and physical characteristics, with Mg·ATP and Mg·PPi as the specific substrates, respectively. The H＋ obtained through the hydrolysis of these substrates is pumped into vacuole, and contributes to the electrochemical proton gradient between cytoplasm and vacuole. The NO3- -N transportation from vacuole to cytoplasm is greatly depended on the electrochemical proton gradient. The NO3- -N transportation from cytoplasm to vacuole is mainly depended on the vacuole H＋/NO3- antiport system, while the symport consisted of vacuole NO3- -N and other anions benefits the transportation of NO3- -N from vacuole to cytoplasm. The transportation of NO3- -N based on the proton pump of vacuole membrane is also affected by the cytoplasm nitrate reductase （NR） activity. Cytoplasm NR can continuously assimilate and reduce NO3- -N, making the NO3- -N accumulated in vacuole more transported into cytoplasm and utilized. This review could provide reference for the further study on the efficient and practicable measures of plant nitrogen utilization, and for improving the NO3- -N reutilization efficiency.