Ultrastructure And Studies On Ca²⁺-ATPase-Localization In Anthers Of Photosensitive Genic Male-sterile Rice

Hubei Photoperiod-sensitive Genic Male-sterile Rice(HPGMR) Nongken 58S was first discovered in China as a spontaneous mutant from a japonica rice(Oryza sativa L. ssp.japonica) cultivar Nongken 58(abbreviated as 58N).Its pollen fertility is regulated by day-length:the pollen is completely sterile under long-day conditions,while the fertility varies from partial to fully fertile under short-day conditions.This characteristic makes it become simplifying for "three-line" hybrids in rice breeding programs and it is very important in practice.In this study,we conducted a systematic cytological observation of the sterile rice Nongken 58S in comparison with its fertile counterpart Nongken 58N.The objective was to identify,at the cytological level,the causal mechanism for the male sterility in the HPGMR.The main results are as the follows:1.The difference of Ca²⁺-ATPase in the anther wall between fertile and sterile riceCa²⁺-ATPase of the plasmalemma,the vacuole membrane and nucleus in the anther wall of the fertile rice are more than the sterile rice.More and more Ca²⁺-ATPase distribute on the Ubisch body of the fertile rice during the pollen development,but no Ca²⁺-ATPase distribute on the Ubisch body of the sterile before the binucleate pollen stage.Ca²⁺-ATPase of the anther wall cells is variational during the fertile anther development,and Ca²⁺-ATPase distribute in the epidermis firstly,subsequently inner. The quantity of Ca²⁺-ATPase in the anther wall and the Ubisch body is more and more during the anther development.The quantity of Ca²⁺-ATPase is the most from the later uninucleate pollen stage to the binucleate pollen stage.Comparatively,little and later Ca²⁺-ATPase is in the anther wall cells of the sterile rice.Some Ca²⁺-ATPase distribute on the plasmalemma of the tapetum cell and the Ubisch body at the binucleate pollen stage.But no Ca²⁺-ATPase distribute on the Ubisch body before the binucleate pollen stage.2.The difference of Ca²⁺-ATPase in the pollen cell between fertile and sterile riceCa²⁺-ATPase Distribution of the fertile and sterile pollen is very different.More and more Ca²⁺-ATPase distribute in the pollen wall,plasmalemma and nucleus from the pre-uninucleate pollen stage to the binucleate pollen stage.But no Ca²⁺-ATPase distribute on the same location in the sterile pollen during the development of the anther except the binucleate pollen stage.The quantity of Ca²⁺-ATPase in the sterile pollen is less than the one in the fertile pollen at the binucleate pollen stage.3.The difference of Ca²⁺-ATPase in the connective tissue between fertile and sterile riceA lot of Ca²⁺-ATPase distribute on the nucleus,plasmalemma and the vacuole membrane of the phloem cell in the fertile connective tissue at PMC meiosis stage,but no Ca²⁺-ATPase distribute in the sterile connective tissue at PMC meiosis stage.A little Ca²⁺-ATPase distribute on the plasmalemma of the phloem cell in the sterile connective tissue at the pre-uninucleate pollen stage.4.Semithin and ultrathin section observation resultsA similar result has been observed by the optical microscope and the electron microscope in the sterile rice Nongken58S.The pollen of the sterile rice abort because of the abnormal development of PMC,exine and tapetum cell.The semithin section results showed that pollen abortion in the PSGMS rice first occurred no later than the PMC stage and continued on in the entire process of pollen development till pollen degradation.This abortive process was closely associated with the abnormal behavior of the tapetum.Although tapetum degeneration in the PSGMS rice initiated at as early as the PMC stage,it proceeded slowly and did not complete until the breakdown of the pollen,which is in sharp contrast to the rapid disintegration of the tapetal layer during late microspore to bicellular pollen stage in the fertile rice.It has been proved that the tapetum cell and the PMC of the sterile rice are abnormal at the PMC stage by the ultrathin section results.The ultrathin section results showed that a little reticulum endoplasmic and mitochondrion and a lot of vesicles are in the tapetum cell at the PMC stage.Some PMC shape is abnormity,little organelle and a lot of vesicles is in the cytoplasm;others lack callose and become disaggregating.Comparatively,exine and intine of the sterile rice is abnormal at the early pollen stage,The shape of the exine is swoln after the mid-microspore stage,intine can not be formed all along.Base on the above results,It is one of reasons for pollen abortion that abnormal Ca²⁺-ATPase distribute on the sterile pollen cell wall and the plasma membrane during the sterile anther development.And Ca²⁺-ATPase from the tapetum cell can not be transmited to the Ubisch body,Ca²⁺ pump does not work for little Ca²⁺-ATPase in the sterile rice,so that it makes pollen abortion with abundant Ca²⁺ in the cytoplasm.