Investigating the Link Between Growth and Pattern in the Arabidopsis Embryo

茎和根尖分生组织在球状植物胚的相对两极发育。尽管人们付出了很多努力，但在被子植物早期发育的基本方面发生改变的突变体，如沿茎/根轴的极性发育，一直是难以捉摸的。研究者推测，这是因为胚胎极性的改变也会导致生长停滞，因此在更大的胚胎致死/停滞突变中发现了相关突变。茎缘转化为根缘（重根胚）或根缘转化为茎缘（重根胚）的突变体在胚胎发生过程中会抑制生长。在对胚胎纯合子的分析中发现了对这一观点的支持（tpl-1）突变。温度敏感的tpl-1突变在限制温度下导致茎向根转化的速率很高。在限制性温度下生长的tpl-1突变胚胎中，有一小类阻滞胚胎在整个球形阶段胚胎中表达根特异性标记（即，在假定的根和芽极中）。为了验证这一假设，Barton博士建议筛选胚胎致死/阻滞突变体，以改变芽极特异性标记（STM报告基因）的表达。然后用额外的根和茎特定标记分析候选突变体，以确定它们是否真的导致极性缺陷。除了这种一般筛选外，PI还将对TPL的强、非温度敏感等位基因进行更有针对性的筛选。这个筛选是为了验证这样一个假设，即一个更强的TPL等位基因将导致一个更渗透的茎到根的转化，并伴随着停滞胚胎比例的增加。这项power资助中描述的研究将使PI有可能进行一系列探索性研究，如果成功，将导致胚胎极性发育中的突变体的分离和表征，这是早期植物发育的基本事件。

Shoot and root apical meristems develop at opposite poles of the globular plant embryo. Despite much effort to obtain them, mutants altered in basic aspects of early development, such as the development of polarity along the shoot/root axis, have been elusive in angiosperm plants. This investigator hypothesizes that this is because alterations in embryo polarity also result in growth arrest and that the relevant mutants are therefore to be found among the much larger class of embryonic lethal/arrest mutants. Mutants in which shoot fates are transformed to root fates (double root embryos) or in which root fates are transformed into shoot fates (double shoot embryos) could arrest growth during embryogenesis. Support for this idea is found in the analysis of embryos homozygous for the topless-1 (tpl-1) mutation. The temperature sensitive tpl-1 mutation causes a high rate of shoot to root transformation at restrictive temperature. Among tpl-1 mutant embryos grown at restrictive temperature is a small class of arrested embryos that express root specific markers throughout the globular stage embryo (i.e., in both presumptive root and shoot poles) To test this hypothesis, Dr. Barton proposes to screen embryonic lethal/arrest mutants for the altered expression of a shoot pole specific marker (an STM reporter gene). Candidate mutants will then be analyzed with additional root and shoot specific markers to determine if they truly result in a polarity defect. In addition to this general screen, the PI will perform a more targeted screen for strong, non-temperature sensitive alleles of TPL. This screen is designed to test the hypothesis that a stronger allele of TPL will result in a more penetrant shoot to root transformation with a concomitant increase in the proportion of arrested embryos. The research described in this POWRE grant will make it possible for the PI to pursue a line of exploratory research that, if successful, should result in the isolation and characterization of mutants in the development of embryonic polarity, a fundamental event in early plant development.