低温胁迫对玉米转绿过程中叶绿素生物合成的影响

The Effects of Low Temperature on Chlorophyll Synthesis during Greening of Maize

【目的】通过对低温胁迫下玉米(Zea mays L.)幼苗转绿过程中叶绿素生物合成中间产物的分析,探究转绿过程中低温调控叶绿素合成的机制。【方法】将黑暗下发芽6 d的玉米幼苗分别置于25℃常温和14℃低温条件下见光48 h,测定见光前和不同温度下见光后幼苗的叶绿素生物合成的主要前体物质积累量,以分析低温对叶绿素生物合成途径的影响。【结果】在25℃常温下,光照促进叶绿素(Chl)和血红素(heme)的合成;而在14℃低温胁迫下,δ-氨基乙酰丙酸(ALA)和Mg-原卟啉Ⅸ(Mg-ProtoⅨ)的积累量显著上升,单卟啉胆色素原(PBG)、尿卟啉原Ⅲ(UrogenⅢ)、粪卟啉原Ⅲ(CoprogenⅢ)、原卟啉Ⅸ(ProtoⅨ)、Mg-原卟啉甲酯(Mpe)、Mg-原卟啉Ⅸ二酯(Mpde)、原叶绿素酸酯(Pchlide)和叶绿素酸酯(Chlide)光照后积累量较常温下低,最终导致叶绿素含量下降,表明ALA向PBG的转化、及Mg-ProtoⅨ向Mpe的转化过程可能受到低温抑制。【结论】14℃低温通过影响ALA向PBG的转化以及Mg-ProtoⅨ向Mpe的转化,抑制玉米的转绿过程。

【Objective】To explore the mechanism of low temperature regulating chlorophyll synthesis in the process of greening by analyzed the intermediate products of chlorophyll biosynthesis in Maize (Zea mays L.) seedlings during greening under low temperature stress.【Method】Maize seedlings germinated in darkness for 6 dayswere exposed to light at 25℃ roomtemperature and 14℃ low temperature for 48 hours, the accumulation of major precursors of chlorophyll biosynthesis in maize seedlings before and after light exposure at different temperatures was measured to analyze the effect of low temperature on the pathwayof chlorophyll biosynthesis.【Result】The content of heme and chlorophyll (Chl) increased sharply after light at 25℃. Under low-temperature stress (14℃),the content of δ-aminolevulinic acid (ALA) and Mg-protoporphyrinⅨ(Mg-ProtoⅨ)increased,and the accumulation of porphobilinogen (PBG),uroporphyrinogen Ⅲ(Urogen Ⅲ),coproporphyrinogen Ⅲ(Coprogen Ⅲ),protoporphyrin Ⅸ(Proto Ⅸ),Mg-protoporphyrin methyl ester (Mpe),Mg-protoporphyrinⅨdimethyl ester (Mpde),protochlorophyllide (Pchlide) and chlorophyllide (Chlide) was lower compared with at 25℃ after illuminating,which led to the decrease of chlorophyll level. It indicated that the conversion of ALA to PBG and Mg-Proto Ⅸ to Mpe may be inhibited by low temperature.【Conclusion】Low temperature (14℃) can obviously inhibit the greening process of maize seedlings by inhibited the conversion of ALA to PBG and Mg-Proto Ⅸ to Mpe.