Abstract
Male sterility induced by a chemical hybridization agent (CHA) is an important tool for utilizing crop heterosis. Monosulphuron ester sodium (MES), a new acetolactate synthase-inhibitor herbicide belonging to the sulphonylurea family, has been developed as an effective CHA to induce male sterility in rapeseed (Brassica napus L.). To understand MES-induced male sterility in rapeseed better, comparative cytological and proteomic analyses were conducted in this study. Cytological analysis indicated that defective tapetal cells and abnormal microspores were gradually generated in the developing anthers of MES-treated plants at various development stages, resulting in unviable microspores and male sterility. A total of 141 differentially expressed proteins between the MES-treated and control plants were revealed, and 131 of them were further identified by MALDI-TOF/TOF MS. Most of these proteins decreased in abundance in tissues of MES-treated rapeseed plants, and only a few increased. Notably, some proteins were absent or induced in developing anthers after MES treatment. These proteins were involved in several processes that may be crucial for tapetum and microspore development. Down-regulation of these proteins may disrupt the coordination of developmental and metabolic processes, resulting in defective tapetum and abnormal microspores that lead to male sterility in MES-treated plants. Accordingly, a simple model of CHA-MES-induced male sterility in rapeseed was established. This study is the first cytological and dynamic proteomic investigation on CHA-MES-induced male sterility in rapeseed, and the results provide new insights into the molecular events of male sterility.
Highlights
Significant heterosis for grain yield and other agronomic traits in rapeseed (Brassica napus L.) is well documented [1]
chemical hybridization agent (CHA)-induced male sterility may circumvent the disadvantages of cytoplasmic male sterility (CMS), genic male sterility (GMS) and SI approaches, such as environmental instability associated with CMS in maintaining male-sterility and/or male-fertility restoration, high risk of disease susceptibility associated with a narrow cytoplasm genetic background [3], intensive labour to remove half-fertile plants from a GMS female parent [4]
We found that the new acetolactate synthase (ALS) inhibitor Monosulphuron ester sodium (MES) can be used as an effective CHA to induce male sterility in rapeseed plants at a concentration about 1% of that needed for its herbicidal activity [7]
Summary
Significant heterosis for grain yield and other agronomic traits in rapeseed (Brassica napus L.) is well documented [1]. Several approaches to the utilization of heterosis have been proposed, including cytoplasmic male sterility (CMS), genic male sterility (GMS), self-incompatibility (SI) and chemical hybridization agents (CHAs) [2]. CHA-induced male sterility in female parents can provide a rapid, flexible and effective system that can enable the development of hybrids from a large number of parental combinations. CHA-induced male sterility may circumvent the disadvantages of CMS, GMS and SI approaches, such as environmental instability associated with CMS in maintaining male-sterility and/or male-fertility restoration, high risk of disease susceptibility associated with a narrow cytoplasm genetic background [3], intensive labour to remove half-fertile plants from a GMS female parent [4].
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