Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow, ID, USA.
Plant Signal Behav. 2011 Apr;6(4):491-3. doi: 10.4161/psb.6.4.14653. Epub 2011 Apr 1.
The presence of callose in sieve plates has been known for a long time, but how this polysaccharide plug is synthesized has remained unsolved. Two independent laboratories have recently reported the identification of callose synthase 7 (CalS7), also known as glucan synthase-like 7 (GSL7), as the enzyme responsible for callose deposition in sieve plates. Mutant plants defective in this enzyme failed to synthesize callose in developing sieve plates during phloem formation and were unable to accumulate callose in sieve pores in response to stress treatments. The mutant plants developed less open pores per sieve plate and the pores were smaller in diameter. As a result, phloem conductivity was reduced significantly and the mutant plants were shorter and set fewer seeds.
筛板中胼胝质的存在由来已久，但这种多糖塞是如何合成的仍未解决。最近，两个独立的实验室报告了纤维素合酶 7（CalS7），也称为葡聚糖合酶样 7（GSL7）的鉴定，它是负责在筛板中沉积胼胝质的酶。这种酶缺陷的突变体植物在韧皮部形成过程中无法在发育中的筛板中合成胼胝质，并且无法在应激处理时在筛孔中积累胼胝质。突变体植物每片筛板上的开放孔较少，孔径较小。因此，韧皮部导率显著降低，突变体植物较矮，结的种子也较少。
