Genetic Recombination and the Function of RNA during Meiosis

通过与百合幼花药体细胞RNA的差减杂交，获得了18个百合小孢子母细胞减数分裂前期表达的DNA克隆。我们正在试图了解这些基因的功能。首先，我们获得了缺失5 '端的完整的LIM 13 DNA，并对所有18个cDNA的基本序列进行了推断。其次，利用针对在大肠杆菌细胞中合成的LIM 15蛋白制备的抗体，将LIM 15 DNA定位于减数分裂前期染色体上，该DNA与大肠杆菌RecA具有高度同源性，RecA是原核生物中同源重组的重要因子。LIM 15蛋白存在于沿着配对和成对染色体的许多点中。这些点的数量远远超过交叉的数量级（X10^3），与之前报道的DNA修复点相一致。另一方面，LIM 14基因在减数分裂细胞中表达，但在绒毡层细胞、四分体和花粉中表达，直至成熟。LIM 14蛋白定位于这些细胞的淀粉粒中，而不定位于茎、叶、根和花药壁细胞的淀粉粒中。LIM 14蛋白富含甘氨酸和丝氨酸。其氨基酸序列与已报道的细胞壁蛋白有一定的相似性。LIM 14蛋白在N-末端肽处具有质体运输信号，如果试图将蛋白质发送到质体或淀粉颗粒，则该信号可以是有用的。

We have 18 cloned DNAs expressed during first meiotic prophase of lily microsporocytes by the substraction hybridization against the somatic RNAs isolated from very young anther. We are trying to understand the function of these genes. First, we have obtained complete LIM13 DNA previously missing the 5'end and concluded the basic sequences of all 18 cDNAs. Secondly, LIM15 DNA showing a high homology with E.coli RecA which is a important factor for homologous recpmbination in prokaryotes, has been localized on meiotic prophase chromosomes by using anibodies prepared against LIM15 protein synthesized in E.cili cells. LIM15 protein are found in many spots along the pairing and paired chromosome. The number of such spots are far more than the number chiasma (order of X10^3) and can be agreeable with the DNA repair spots reported earlier. It has been found that RAD52 and other RAD proteins co-localize with LIM15 and we consider this as the suggestive evidence that recombination requires than one protein.On the other hand, LIM14 gene is expressed in meiotic cells but the product has been detected in tapetal cells, tetrads and in pollen till the maturity. LIM14 protein is localized in the staarch granules of those cells but not in the starch granules in stem, leaf, root and the anther wall cells. The LIM14 protein is rich in glycine and serine contents. It has some similarity in the amino acid sequence with the reported cell wall protein. LIM14 protein has a plastid-transport signal at the N-terminal peptide, which can be useful if one trys to send a protein to the plastids or starch granules.