腺苷二磷酸葡萄糖焦磷酸化酶活性对小麦K、V、T型不育系育性及籽粒形成的影响

为进一步探寻小麦不育系的不育机制和籽粒不饱满的生理机制，以冀5418核基因为遗传背景，对同核异质K、V、T型不育系叶片、幼穗和籽粒中的腺苷二磷酸葡萄糖焦磷酸化酶(ADP-glucose pyrophosphorylase, AGPase)活性和淀粉积累量进行了动态观测，并与各自的保持系进行了比较。在雌雄蕊原基分化期, 不育系幼穗中AGPase活性较保持系高9.33~27.94 μmol g^-1 FW h^?1, 差异达极显著水平(F=133.81, P<0.0001); 而在四分体期, 不育系幼穗中该酶活性极显著低于保持系(F=13.97~75.20, P<0.0001)，差异为4.27~7.44 μmol g^-1 FW h^?1。雌雄蕊原基分化期至四分体时期，不育系叶片中AGPase活性较保持系高7.39~80.77 μmol g^-1 FW h^?1，差异极显著(F=135.76~5454.28,P<0.0001)。不育系强、弱势粒中总淀粉、直链淀粉和支链淀粉积累量、AGPase平均活性、淀粉含量及直/支比均极显著低于保持系，且这些指标均表现为强势粒显著高于弱势粒。Logistic方程显示，不育系籽粒淀粉积累量的减少主要由淀粉积累速率降低引起；籽粒AGPase活性与淀粉积累速率显著或极显著正相关(r=0.4460~0.7150, P=0.0004~0.0487)；灌浆期, 叶片中AGPase活性与光合速率呈负相关(r=?0.28634, P=0.2823)。因此，雄性不育的可能原因是雌雄蕊原基分化期幼穗和叶片中AGPase活性高，幼穗发育所需能量供应不足；而四分体期幼穗AGPase活性低，影响花粉中淀粉积累。不育系对籽粒AGPase活性具有明显的不良胞质效应，降低ADPG供应水平，影响淀粉的积累，以及旗叶AGPase活性对净光合速率的不良影响，是籽粒不饱满的重要原因之一。

Effects of ADP-Glucose Pyrophosphorylase Activity on Sterility and Development of Grain in K, V, and T-Cytoplasmic Male Sterile Lines in Wheat

Cytoplasmic male-sterile (CMS) lines, especially K (Aegilops kotchyi), V (Aegilops ventricosa), and T (Triticum timopheevi) types of cytoplasms, are of high value in heterosis utilization in wheat (Triticum aestivum L.). The sterile mechanisms of these CMS types have been focused in hybrid wheat research. As a key and rate-limiting starch biosynthetic enzyme, ADP-glucose pyrophosphorylase (AGPase) is considered to play an important role in the sterility of CMS lines. For gaining an insight into the physiological basis of the sterility in CMS lines of wheat, the activities of AGPase in leaves, young spikes, and grains were measured in K, V, and T types of isogenic CMS lines (Ji 5418 background) at different growth stages, and compared with those of their maintainer line. The dynamic accumulations of starch, amylose, and amylopectin were also investigated in both superior (the first and the second grains in a spikelet) and inferior (grains except for the first and the second grains in a spikelet) grains. In young spikes, the AGPase activities of the three CMS lines were significantly higher (F = 133.81, P < 0.0001) with the differences of 9.33 - 27.94 μmol g^-1 FW h^-1 at floret primordium stage, and significantly lower (F = 13.97 - 75.20, P < 0.0001) by 4.27 - 7.44 μmol g^-1 FW h^-1 at tetrad stage as compared with the maintainer line. From floret primordium to tetrad stage, the CMS lines had continuously higher level of AGPase activities in leaves than the maintainer line, with the differences ranged from 7.39 to 80.77 μmol g^-1 FW h^-1 (F = 135.76 - 5454.28, P < 0.0001). Compared with the maintainer line, the three CMS lines all presented lower accumulations (P < 0.05) of starch, amylose and amylopectin in grain. The starch content and AGPase activity in superior grains were significantly higher than those in inferior grains for CMS lines. The dynamic accumulations of starch in superior and inferior grains fitted Logistic equations, and positively correlated with the starch accumulation rate (r = 0.4460 - 0.7150, P = 0.0004 - 0.0487). The AGPase activity in leaves had an insignificantly negative correlation with net photosynthetic rate. In conclusion, the male sterility is probably in relation to the insufficiency of energy in leaves and young pikes at floret primordium stage resulting from the high AGPase activity, and the low accumulation of starch in pollens at tetrad stage caused by low AGPase activity in young spikes. The sterile cytoplasm has a negative effect on AGPase activity, resulting in decreases of ADPG level and starch accumulation in grains. Besides, the negative effect of AGPase activity on net photosynthetic rate in flag leaves may result in unfilled grains in CMS lines.