研究結果顯示，無論以單獨MSO處理大豆植株，或是經過SA前處理的大豆植株，其結果都是造成植物死亡，但是兩者細胞凋亡的模式並不相同，前者類似老化死亡，後者為似PCD的死亡。尤其在SA與MSO的交互作用影響下，反而使葉片的細胞結構遭受破壞加速死亡。所以，對於外加SA的濃度於大豆植株，是否能夠減緩MSO對植物所受到的傷害之假設，本研究初步結果顯示是無法成立的。 Glutamine synthetase (GS) is a key enzyme in N metabolism and it catalyses the synthesis of Glutamine (Gln) from glutamic acid, ATP, and NH4+. L-Methionine sulfoximine (MSO) is a glutamate analogue, it is also the GS inhibitor. Salicylic acid (SA) is an endogenous growth regulator of phenolic. At the same time, SA can induce a protective effect on plants under stress. Convincing data have been obtained on the SA-induced in the resistance of barley seedlings to heavy metal and herbicide.
This research is divided into two parts to confer what influences on soybean treated by MSO and SA. First, we demonstrate the effects on soybean seeds treated by MSO alone according to the expression of GS gene, including GS activity and GS biosynthesis. Second, we use pre-treated SA of soybean seedlings to determine if SA could reduce the damages of plants caused by MSO.
By applying MSO to soybean seeds, there are no effects on budding of them. But the growth and development of roots and shoots are inhibited by MSO. GS activity of roots, shoots and cotyledons decrease by increasing MSO concentration. But the GS protein is not only decreased but also accumulated with increasing MSO concentration. This is may be that MSO is converted to MSO-phosphate which mimics the tetrahedral intermediate formed at the active site of GS by the reaction of an enzyme bound gamma-glutamyl phosphate with ammonia.
On the other hand, the plants that are treated by MSO alone or pre-treated SA all died. But the cell apotosis between different treatments aren’t the same. When we only applied MSO to the soybean seedlings, the plants would be senescence naturally. But when we pre-treated SA before exposure MSO, the plants senescence faster than treated MSO alone. According to the serious information, including GS activity and protein biosynthesize. Senescence of pre-treated SA soybean seedlings is similar to program cell death (PCD). We consider the soybean is damaged by MSO on GS, and we try to reduce the damage by pre-treated SA to soybean. But all the results show that can’t reduce damages caused by MSO.
